Medical therapy target definition

ABSTRACT

In some examples, a system may include a plurality of electrodes, electrical stimulation circuitry, and a controller. The controller may be configured to select one or more parameters of therapy to be delivered to a brain of a patient and to control the electrical stimulation circuitry to deliver the therapy to the brain of the patient based on the selected parameters and via a first one or more electrodes of the plurality of electrodes. The parameters may be defined based on a first plurality of electrical signals sensed at a plurality of different positions within the brain of the patient when electrical stimulation is not delivered at each of the positions and a second plurality of electrical signals sensed at each of the plurality of different positions within the brain of the patient in response to electrical stimulation delivered at each of the positions at a plurality of different intensities.

TECHNICAL FIELD

The disclosure relates to defining a target for medical therapy.

BACKGROUND

Implantable medical devices, such as electrical stimulators, may be usedin different therapeutic applications. In some therapy systems, animplantable electrical stimulator delivers electrical stimulationtherapy to a target tissue site within a patient with the aid of one ormore medical leads that include electrodes. In addition to or instead ofelectrical stimulation therapy, a medical device may deliver atherapeutic agent to a target tissue site within a patient with the aidof one or more fluid delivery elements, such as a catheter.

During a programming session, which may occur during implant of themedical device, during a trial session, or during a follow-up sessionafter the medical device is implanted in the patient, a clinician maygenerate one or more therapy programs that provide efficacious therapyto the patient, where each therapy program may define values for a setof therapy parameters. A medical device may deliver therapy to a patientaccording to one or more stored therapy programs. In the case ofelectrical stimulation, the therapy parameters may include theconfiguration of electrodes and/or electrical stimulation intensitiesused to deliver the electrical stimulation therapy.

SUMMARY

In general, the disclosure is directed toward defining a therapy target,which may be a portion of the anatomy that is targeted to receivetherapy, and delivering therapy based on the therapy target definition.In deep brain stimulation (DBS), for example, a therapy targetdefinition may characterize a source of oscillation within a brain of apatient, such as a source of oscillations in a specific frequency rangeor band that may be associated with one or more diseases or disorders;for example, a source of oscillation in the beta frequency band may beassociated with certain symptoms of Parkinson's disease.

In some examples, the therapy target definition may correspond to aspatial characteristic, such as size, shape, volume, origin and/orlocation of the oscillation signal source within the brain. In someexamples, the therapy target definition may be used by a medical devicesystem to define parameters for delivery of electrical stimulation toalleviate symptoms of the diseases or disorders associated with thesource. In some examples, the parameters may be selected at least inpart as a function of the therapy target definition, e.g., as a functionof a spatial characteristic of the source or affected area representedby the therapy target definition.

In other examples, the therapy target definition may be used by amedical device system to define therapy for forming one or more lesionscorresponding to the spatial extent of an oscillation signal source, tomonitor changes, such as growth, in the spatial extent of theoscillation signal source, to monitor for movement of a lead or othermedical component with respect to the oscillation signal source, or inany other suitable manner according to particular needs.

In some examples, defining the therapy target may comprise definingparameters for delivering therapy, including, for example, selectingelectrodes for delivery of electrical stimulation and/or selectingintensities of electrical stimulation delivered by the selectedelectrodes. For example, selected electrodes and selected intensitiesmay define the therapy target and directly form parameters for deliveryof electrical stimulation. In other examples, the therapy target may bedefined and then the stimulation parameters may be selected based on thetherapy target definition.

The therapy target may be defined by sensing electrical signals at aplurality of positions within a brain, delivering electrical stimulationat the plurality of positions within the brain, sensing electricalsignals in response to the delivered electrical signals at the pluralityof positions, and defining the therapy target based on the electricalsignals sensed before delivery of electrical stimulation and in responseto the delivery of the electrical stimulation. Throughout thisapplication, references to an oscillation signal source or source may beused to refer to an origin of oscillation within the brain and/or anaffected area of the brain that is impacted by the origin and thesystems and methods described may be used to define a spatial extent ofthe origin and/or the affected area.

Defining a therapy target that corresponds to a spatial extent of asource of beta oscillation or other physiological signals may providefor improved treatment of symptoms caused by or associated withoscillations emitted by the source. For example, informationcorresponding to the spatial extent of the source may be used to deliverappropriate electrical stimulation with appropriate parametersincluding, for example, position, amplitude, frequency, and/or pulsewidth, to form a lesion corresponding to the spatial extent of thesource, perform plasticity inductions, perform drug infusions, morebroadly map states and extents of brain dysfunction, monitor for changesin the spatial extent of the source, and/or monitor for movement of alead with respect to the source. The described method of defining thetherapy target may be performed, in some examples, using a single lead,reducing risks associated with multiple leads including, for example,increased risk of brain tissue damage or hemorrhage.

In one example, the disclosure is directed to a method for deliveringtherapy to a patient. The method may include selecting one or moreparameters of therapy to be delivered to a brain of a patient. Theparameters may be defined based on a first plurality of electricalsignals sensed at each of a plurality of different positions within thebrain of the patient when electrical stimulation is not delivered ateach of the positions; and a second plurality of electrical signalssensed at each of at least a subset of the plurality of differentpositions within the brain of the patient in response to electricalstimulation delivered at each of the at least the subset of thepositions at a plurality of different intensities. The method mayinclude delivering the therapy to the brain of the patient based on theselected parameters.

In another example, the disclosure is directed to a system fordelivering electrical stimulation. The system may include a plurality ofelectrodes, electrical stimulation circuitry, and a controllerconfigured to select one or more parameters of therapy to be deliveredto a brain of a patient. The parameters may be defined based on a firstplurality of electrical signals, sensed at a plurality of differentpositions within the brain of the patient when electrical stimulation isnot delivered at each of the positions, and a second plurality ofelectrical signals, sensed at each of at least a subset of the differentpositions within the brain of the patient in response to electricalstimulation delivered at each of the at least a subset of the differentpositions at a plurality of different intensities. The controller may befurther configured to control the electrical stimulation circuitry todeliver the therapy to the brain of the patient based on the selectedparameters and via a first one or more electrodes of the plurality ofelectrodes.

In yet another example, the disclosure is directed to a system fordelivering electrical stimulation. The system may include means forselecting one or more parameters of therapy to be delivered to a brainof a patient. The parameters may be defined based on a first pluralityof electrical signals, sensed at a plurality of different positionswithin the brain of the patient when electrical stimulation is notdelivered at each of the positions, and a second plurality of electricalsignals, sensed at each of at least a subset of the different positionswithin the brain of the patient in response to electrical stimulationdelivered at each of the at least a subset of the different positions ata plurality of different intensities. The system may further includemeans for delivering the therapy to the brain of the patient and meansfor controlling the means for delivering therapy to deliver the therapyto the brain of the patient based on the selected parameters.

The details of one or more embodiments of the disclosure are set forthin the accompanying drawings and the description below. Other features,objects, and advantages of the disclosure will be apparent from thedescription and drawings, and from the claims.

BRIEF DESCRIPTION OF DRAWINGS

FIGS. 1A and 1B are conceptual diagrams illustrating an example deepbrain stimulation (DBS) system.

FIG. 2 is a functional block diagram illustrating components of anexample medical device.

FIG. 3 is a functional block diagram illustrating components of anexample medical device programmer.

FIGS. 4A and 4B are conceptual diagrams illustrating exampleconfigurations for sensing electrical signals at a plurality ofdifferent positions within a brain of a patient.

FIG. 5 is a graph illustrating electrical signals sensed at theplurality of different positions within a brain of a patient for each ofa triangular source, a spherical source, and a point source.

FIGS. 6A, 6B, and 6C are diagrams illustrating example electrodeconfigurations for delivering electrical stimulation at a plurality ofdifferent intensities at each of a plurality of different positionswithin a brain of a patient and sensing electrical signals at each ofthe different positions in response to the electrical stimulation.

FIGS. 7A and 7B are diagrams illustrating cross-sectional views ofexample electrode configurations for delivering electrical stimulationat a plurality of different intensities at each of a plurality ofdifferent positions within a brain of a patient and sensing electricalsignals at each of the different positions in response to the electricalstimulation taken along lines 7A-7A and 7B-7B of FIG. 6A, respectively.

FIGS. 8A and 8B are diagrams illustrating another example electrodeconfiguration for delivering electrical stimulation at a plurality ofdifferent intensities at each of a plurality of different positionswithin a brain of a patient and sensing electrical signals at each ofthe different positions in response to the electrical stimulation.

FIG. 9 is a flow diagram of an example technique for defining a therapytarget, selecting therapy parameters based on the therapy targetdefinition, and delivering therapy to a brain of a patient based on theselected parameters.

FIG. 10 is a flow diagram of an example technique for defining a therapytarget, selecting therapy parameters based on the therapy targetdefinition, and delivering therapy to a brain of a patient based on theselected parameters.

DETAILED DESCRIPTION

FIGS. 1A and 1B are conceptual diagrams illustrating an example deepbrain stimulation (DBS) system 102. System 102 may deliver electricalstimulation therapy to tissue in the brain of a patient 104 to control apatient condition, such as a movement disorder, neurodegenerativeimpairment, a mood disorder or a seizure disorder of the patient 104.Patient 104 ordinarily will be a human patient. In some cases, however,therapy system 102 may be applied to other mammalian or non-mammalian,non-human patients. While movement disorders and neurodegenerativeimpairment are primarily referred to herein, in other examples, therapysystem 102 may provide therapy to manage symptoms of other patientconditions, such as, but not limited to, seizure disorders (e.g.,epilepsy) or mood (or psychological) disorders (e.g., major depressivedisorder (MDD), bipolar disorder, anxiety disorders, post traumaticstress disorder, sleep disorders, dysthymic disorder, Tourette'ssyndrome, addiction disorders, and obsessive-compulsive disorder (OCD)).

A movement disorder or other neurodegenerative impairment may includesymptoms such as, for example, muscle control impairment, motionimpairment or other movement problems, such as rigidity, bradykinesia,rhythmic hyperkinesia, nonrhythmic hyperkinesia, and akinesia. In somecases, the movement disorder may be a symptom of Parkinson's disease.However, the movement disorder may be attributable to other patientconditions. Although movement disorders are primarily referred tothroughout the remainder of the disclosure, the therapy systems andmethods described herein are also useful for managing (e.g., controllingpatient symptoms) other patient conditions, such as neurodegenerativeimpairment or mood disorders.

Beta oscillations or oscillations in other frequency ranges in thesubthalamic nucleus (“STN”) of Parkinson's Disease (“PD”) patients maybe a physiomarker or biomarker related to PD motor performance and maybe related to PD and disease progression. Similar oscillatory activitiesin brain tissue may be related to other neurological dysfunctions.Different movement disorder symptoms may be detected based on biomarkersrelated to different frequency bands of a bioelectrical brain signal. Anexample of frequency bands is shown in Table 1 below:

TABLE 1 Frequency (f) Band Hertz (Hz) Frequency Information f < 5 Hz δ(delta frequency band)  5 Hz ≦ f ≦ 10 Hz α (alpha frequency band) 10 Hz≦ f ≦ 30 Hz β (beta frequency band)  50 Hz ≦ f ≦ 100 Hz γ (gammafrequency band) 100 Hz ≦ f ≦ 200 Hz high γ (high gamma frequency band)

System 102 may select the frequency band to monitor based on thepatient's symptoms. While for ease of reference, the followingdiscussion describes examples of using beta activity as a biomarker ofinterest, it will be understood that one or more other frequency bands,or ratios between two frequency bands, may be used in addition to, orinstead of, the beta band frequency according to examples of thisdisclosure.

The goal during DBS implantation and programming may be to set the leadposition and stimulation parameters such that they maximally suppressbeta or other oscillatory activity. Studies demonstrate betaoscillations may not come from a point source, but rather the source mayextend for ranges from 0.5 mm to 3.5 mm along the DBS lead trajectory.See Zaidel A, Spivak A, Grieb B, Bergman H, Israel Z. Subthalamic spanof beta oscillations predicts deep brain stimulation efficacy forpatients with Parkinson's disease. Brain 133 (Pt 7): 2007-2021, 2010.PMID 20534648.). Further, the spatial extent of the beta activity maypredict disease severity, disease progression or the clinical outcomeusing DBS therapy. A larger spatial extent of beta activity along thelead trajectory may be correlated with improved outcomes for DBS. Forthese reasons it may be desirable to quantify the spatial extent of betaoscillations in the brain and, for DBS therapy, deliver stimulation tocover the entire spatial extent of the beta oscillations. Similarmapping may be useful for other therapeutic approaches (such as lesions,plasticity inductions, drug infusions or more broadly mapping states andextents of brain dysfunction).

One potential problem for DBS is difficulty in determining the numberand/or intensity of specific electrical contacts to deliver electricalstimulation for DBS therapy. Relying solely on sensing information maynot allow determination of the spatial distribution of the source. Forexample, multiple “shapes” or patterns of source distributions mayproduce identical profile of recorded potentials at the electrodecontacts, as discussed below with reference to FIGS. 4A and 4B. To solvethis problem, a combination of both sensing and stimulation may be usedto adequately map the distribution of the source. In this manner, thespatial extent or pattern of source distribution within the brain may bedetermined. And for DBS, effective stimulation can be delivered to thedistributed source to be maximally effective as a therapy. With thespatial distribution mapped, appropriate stimulation contacts andstimulation parameters (intensity, frequency and pulse width) may beapplied to provide effective therapy.

Current DBS practice permits the measurement of beta or other activityalong the trajectory of the DBS lead by recording local field potentialsor micro electrode recordings (MERs) while moving the lead towards thestimulation target or along the length of an implanted lead. However,this method may not allow sensing of the “width” or radial extent of thespatial signal at an angle perpendicular to the lead axis. One conceptto solve this problem may be inserting multiple test leads/electrodes to“triangulate” the extent and boundaries of beta activity. But thismethod may carry the increased risk of brain tissue damage or hemorrhagecaused by multiple lead tracks. The method described below relies onlyupon a single lead track, therefore reducing risk of multiple leads.

Therapy system 102 may include medical device programmer 120,implantable medical device (IMD) 110, lead extension 116, and lead 114with electrodes 118 a, 118 b, 118 c, and 118 d. In the examples shown inFIGS. 1A and 1B, electrodes 118 of lead 114 may be positioned to deliverelectrical stimulation to a tissue site within brain 106, such as a deepbrain site under the dura mater of brain 106 of patient 104. Brain 106may include a region of tissue that operates as a source of brain signaloscillations, such as beta band oscillations. In addition to temporalcharacteristics such as the frequency of oscillation, this source may becharacterized by spatial characteristics, such as a position, spatialsize and spatial shape. One example of such a source is represented inFIG. 1A with reference numeral 108. Source 108 may be a source of betaoscillations within brain 106, or a source of other oscillations inother therapy applications and may include an origin of the oscillationand/or an affected area of the brain. In some examples, source 108 mayextend along the length of lead 114 in a range of approximately 0.5 mmto 3.5 mm.

In some examples, delivery of stimulation to one or more regions ofbrain 106, such as the subthalamic nucleus, globus pallidus or thalamus,may be an effective treatment to manage movement disorders, such asParkinson's disease. Electrodes 118 may also be positioned to sensebioelectrical brain signals within brain 106 of patient 104. In someexamples, some of electrodes 118 a, 118 b, 118 c, and 118 d may beconfigured to sense bioelectrical brain signals and others of electrodes118 a, 118 b, 118 c, and 118 d may be configured to deliver electricalstimulation to brain 106. In other examples, all of electrodes 118 a,118 b, 118 c, and 118 d may be configured to both sense bioelectricalbrain signals and deliver electrical stimulation to brain 106, e.g., ona selective basis. Electrodes 118 a, 118 b, 118 c, and 118 d may includeany suitable types of electrodes including, for example, ringelectrodes, segmented electrodes, or pad electrodes. Each of electrodes118 a, 118 b, 118 c, and 118 d may be used to refer to a singleelectrode, an electrode segment, or a group of electrodes or electrodesegments corresponding to one or more axial and/or circumferentialpositions on lead 114.

IMD 110 may include an electrical stimulation circuitry 204 (FIG. 2)that generates and delivers electrical stimulation to patient 104 viaone or more of electrodes 118 a, 118 b, 118 c, and 118 d of lead 114 andsensing circuitry 206 senses bioelectrical signals within brain 106 viaone of more electrodes 118 a, 118 b, 118 c, and 118 d of lead 114. Insome examples, the bioelectrical signals sensed within brain 106 mayreflect changes in electrical current produced by the sum of electricalpotential differences across brain tissue. Examples of bioelectricalbrain signals include, but are not limited to, electrical signalsgenerated from local field potentials (LFP) sensed within one or moreregions of brain 106, such as an electroencephalogram (EEG) signal, oran electrocorticogram (ECoG) signal. Local field potentials, however,may include a broader genus of electrical signals within brain 106 ofpatient 104. LFP signals may have frequency content spanning one or morefrequency ranges, including beta band signals, gamma band signals,and/or other signal ranges such as those discussed above that mayprovide information useful for defining a therapy target, which may be aportion of the anatomy that is targeted to receive therapy,corresponding to source 108. Various techniques may be used to extractthe frequency ranges. For instance, band-pass filters may be used toextract selected frequency ranges from the time-domain LFP signal andthe amplitude (e.g., in microvolts) or power level of the signal in theselected frequency range may be measured. For example, the relative betaband power may be determined as a ratio of the beta band power to avoltage amplitude of the signal. The voltage amplitude may be a mean ormedian voltage amplitude of the signal over a predetermined range oftime, such as about ten seconds to about two minutes, although othertime ranges are also contemplated. The voltage amplitudes of thebioelectrical brain signals may be calibration coefficients that helpminimize variability between the power levels of the bioelectrical brainsignals in a particular frequency band that is attributable todifferences in the overall signal power level.

In some examples, transforms such as a fast Fourier transforms (FFTs)may be used to convert the LFP or other time-domain signal to thefrequency domain so that the signal level in a particular frequency bandmay be determined. As one example, a power spectral density (PSD) may bedetermined in microvolts squared per Hertz (μv²/Hz) for a particularfrequency band based on the frequency domain data.

In some examples, microelectrode recording (MER) data of the typegenerated from acute use/mapping leads or microelectrodes provided onchronic leads may be used in additional to, or instead of, the LFP data.In other examples, microelectrodes may be used to record macro LFPs foruse according to the disclosed techniques. Other data from other typesof recording methodologies may be used. Thus, the current disclosure isnot limited by any particular structure or technique used to record thesensed signals, and any technique suitable for recording the signals iscontemplated.

In some examples, the bioelectrical brain signals may be sensed withinthe same region of brain 106 as a target tissue site for the electricalstimulation. As previously indicated, these tissue sites may includetissue sites within the thalamus, subthalamic nucleus or globus pallidusof brain 106, as well as other target tissue sites. The specific targettissue sites and/or regions within brain 106 may be selected based onthe patient condition. Thus, in some examples, both a stimulationelectrode combination and sense electrode combinations may be selectedfrom the same set of electrodes 118 a, 118 b, 118 c, and 118 d. In otherexamples, the electrodes used for delivering electrical stimulation maybe different than the electrodes used for sensing bioelectrical brainsignals.

In some examples, the delivery of electrical stimulation and sensing ofelectrical signals may be used to define a therapy target and to delivertherapy based on the therapy target definition. In some examples,defining the therapy target may comprise defining parameters fordelivering therapy, including selecting electrodes for delivery ofelectrical stimulation and/or selecting intensities of electricalstimulation, which may be a function of amplitude, pulse width, andpulse rate. In such an example, sensed signals and intensities selectedto define the parameters may be representative of a therapy target thatis a function of a spatial extent of an oscillatory source, and alsoserve as parameters for delivery of electrical stimulation therapy. Inother examples, the therapy target may be defined and then theparameters may be selected based on the therapy target definition.Source 108, for example, may be a source that exhibits a detectablesignal characteristic, such as beta oscillations and IMD 110 may be usedto define a therapy target corresponding to a spatial extent of source108 and to deliver therapy based on the therapy target definition.Movement disorders may be promoted by beta band oscillations emitted bytissue associated with a source, such as source 108. As will bedescribed, defining a therapy target that characterizes source 108,e.g., in terms of position, spatial size and/or spatial shape, maypermit selection of therapy parameters to more specifically target thesource and more effectively counteract the beta band oscillationsemitted from the source. Different signal characteristics may be used tocharacterize sources for different therapies, for example, a differentfrequency band may be of interest for a different therapy.

In some instances, the source may exhibit a detectable signalcharacteristic in the time domain rather than the frequency domain. Forinstance, an instantaneous or time-averaged signal amplitude of an LFPthat exceeds or is below a high or low threshold value, respectively,may be monitored in response to therapy to determine a spatial extent ofsource 108. As another example, a waveform morphology, as may bedetermined based on template matching or some other mechanism, may bemonitored to determine spatial extent of source 108. As yet anotherillustration, EEG signals may be used to determine whetherepileptic-type activity is responding to stimulation to define spatialextent of the source.

Thus, while the beta band oscillations are used as an example, anysensed characteristic of a signal in the time or frequency domains thatis indicative of responsiveness to stimulation (e.g., responsiveness ofaffected tissue to stimulation) may be monitored to define a therapytarget. Algorithms for defining a therapy target corresponding to aspatial extent of source 108 are described with reference to FIGS.4A-10.

In some examples, the therapy target may be defined during a programmingsession before the implantation of IMD 110, including duringimplantation of lead 114 in patient, as shown in FIG. 1A. As shown inFIG. 1A, a motor 122 may be used to position lead 114 and the therapytarget may be defined during movement of lead 114 within patient 104 by,for example, motor 122. In some examples, the therapy target may bedefined during a programming session after implantation of IMD 110 andlead 114 in patient 104, as shown in FIG. 1B. The therapy target mayalso be subsequently defined at later times to monitor for changes inthe therapy target and/or movement of lead 114. For example, a therapytarget may be initially defined at an initial definition time and atherapy target may be defined at a later definition time. Changes indefinition from the initial time to the later time may indicate changesin source 108, such as, for example, growth or retraction of source 108,and/or may indicate movement of lead 114 with respect to source 108.Although system 102 is described as including an IMD 110 and a separateprogrammer 120, system 102 may also be implemented with a device notintended to be implanted in patient 104 and/or without a separateprogrammer 120. For example, system 102 may be used in a procedureincluding implantation of lead 114 in brain 106, definition of thetherapy target corresponding to source 108, delivery of therapy based onthe therapy target definition, such as, for example, forming a lesion inbrain 106 corresponding to the therapy target definition and thuscorresponding to source 108, and removal of lead 114 from brain 106.Such a procedure may, for example, use motor 122 for positioning of lead114 during the procedure including, for example, during definition ofthe therapy target and/or during forming of the lesion. Defining atherapy target corresponding to a spatial extent of source 108 mayfurther be used for other therapeutic approaches including, for example,plasticity inductions, drug infusions, and/or more broadly mappingstates and extents of brain dysfunction.

In some examples, the process may be performed while simultaneouslyforming a lesion. For example, the process may be performed to monitorthe source while forming the lesion. In other examples, the process maybe performed to determine a 3-dimensional mapping of the source, themapping may be stored, and the lesion may be formed based on the storedmapping.

IMD 110 may be implanted within a subcutaneous pocket above theclavicle, or, alternatively, the abdomen, back or buttocks of patient104, on or within a cranium or at any other suitable site within patient104. Generally, IMD 110 is constructed of a biocompatible material thatresists corrosion and degradation from bodily fluids. IMD 110 maycomprise a hermetic housing to substantially enclose components, such asa controller, therapy module, and memory.

Implanted lead extension 116 may be coupled to IMD 110 via a connector(also referred to as a connector block or a header) of IMD 110. In theexample of FIG. 1B, after IMD 110 has been implanted, e.g., chronically,lead extension 116 traverses from the implant site of IMD 110 and alongthe neck of patient 104 to the cranium of patient 104 to access brain106. Lead 114 may be implanted within the right or left hemisphere ofpatient 104 in order to deliver electrical stimulation to one or moreregions of brain 106, which may be selected based on the patientcondition or disorder controlled by therapy system 102, including one ormore regions suspected or concluded to include source 108. The specifictarget tissue site and the stimulation electrodes used to deliverstimulation to the target tissue site, however, may be selected, e.g.,using the algorithms described herein, e.g., with respect to FIGS.4A-10. Other implant sites for lead 114 and IMD 110 are contemplated.For example, IMD 110 may be implanted on or within the cranium ofpatient 104, in some examples.

Lead 114 may be positioned to deliver electrical stimulation to one ormore target tissue sites within brain 106 including source 108 to managepatient symptoms associated with a movement disorder of patient 104.Lead 114 may be implanted to position electrodes 118 a, 118 b, 118 c,and 118 d at desired locations of brain 106 through respective holes inthe patient's cranium. Lead 114 may be placed at any location withinbrain 106 such that at least one of electrodes 118 a, 118 b, 118 c, 118d are capable of providing electrical stimulation to target tissue siteswithin brain 106 during treatment. For example, electrodes 108 a, 108 b,108 c, and 108 d may be surgically implanted under the dura mater ofbrain 106 or within the cerebral cortex of brain 106 via a burr hole inthe cranium of patient 104, and electrically coupled to IMD 110 via lead114.

Example techniques for delivering therapy to manage a movement disorderare described in U.S. Patent Application Publication No. 2009/0099627 byMolnar et al., entitled, “THERAPY CONTROL BASED ON A PATIENT MOVEMENTSTATE,” filed on Sep. 25, 2008, which is incorporated herein byreference in its entirety. In some examples described by U.S. PatentApplication Publication No. 2009/0099627 by Molnar et al., a brainsignal, such as an EEG or ECoG signal, may be used to determine whethera patient is in a movement state or a rest state. The movement stateincludes the state in which the patient is generating thoughts ofmovement (i.e., is intending to move), attempting to initiate movementor is actually undergoing movement. The movement state or rest statedetermination may then be used to control therapy delivery. For example,upon detecting a movement state of the patient, therapy delivery may beactivated in order to help patient 104 initiate movement or maintainmovement, and upon detecting a rest state of patient 104, therapydelivery may be deactivated or otherwise modified.

In the example shown in FIGS. 1A and 1B, electrodes 118 a, 118 b, 118 c,and 118 d of lead 114 are shown as ring electrodes. Ring electrodes maybe used in DBS applications because they are relatively simple toprogram and are capable of delivering an electrical field to any tissueadjacent to electrodes 118 a, 118 b, 118 c, and 118 d. In otherexamples, electrodes 118 a, 118 b, 118 c, and 118 d may have differentconfigurations. For example, in some examples, at least some of theelectrodes 118 a, 118 b, 118 c, and 118 d of lead 114 may have a complexelectrode array geometry that is capable of producing shaped electricalfields. The complex electrode array geometry may include multipleelectrodes (e.g., partial ring or segmented electrodes) around the outerperimeter of each lead 114, rather than one ring electrode. For example,electrode segments may be positioned at the same axial position but atdifferent angular positions around the circumference of the lead. Setsof electrode segments may be provided at different axial positions,e.g., such that sets of two, three, four or more electrode segments formdiscontinuous rings or partial rings around the lead circumference atdifferent axial positions. In some examples, ring electrodes andsegmented electrodes may be combined on a lead, such that ringelectrodes are formed at some axial positions and segmented electrodesare formed at other axial positions. An example is a 1-3-3-1configuration in which a first ring electrode is formed on a lead at afirst axial position, a first set of three electrode segments are formedat a second axial position, a second set of three electrode segments areformed at a third axial position and a second ring electrode is formedat a fourth axial position, where the first, second, third and fourthpositions are arranged in axial order along the length of the lead.

With segmented electrodes, electrical stimulation may be directed in aspecific direction from lead 114 to enhance therapy target definition,as will be described with reference to FIGS. 4A-10 and FIGS. 6A and 6Bin particular, and/or therapy efficacy and reduce possible adverse sideeffects from stimulating a larger volume of tissue. In some examples, ahousing of IMD 110 may include one or more stimulation and/or sensingelectrodes. In alternative examples, lead 114 may have shapes other thanelongated cylinders as shown in FIGS. 1A and 1B. For example, lead 114may be a paddle lead, spherical lead, bendable lead, or any other typeof shape effective in treating patient 104, including defining a therapytarget corresponding to source 108 and delivering therapy based on thetherapy target definition, as described with reference to FIGS. 4A-10,and/or minimizing invasiveness of lead 114.

In the example shown in FIGS. 1A and 1B, IMD 110 includes a memory(shown in FIG. 2) to store therapy target definition programs fordefining a therapy target and may, after defining the therapy target,store one or more therapy programs that may each define a set of therapyparameters for delivering therapy based on the therapy targetdefinition. In some examples, IMD 110 may select a therapy program fromthe memory based on various parameters, such as a detected patientactivity level, a detected patient state, based on the time of day, andthe like. IMD 110 may generate electrical stimulation based on theselected therapy program to manage the patient symptoms associated witha movement disorder.

In some examples, defining the therapy target may comprise definingparameters for delivering therapy, including selecting electrodes fordelivery of electrical stimulation and/or selecting intensities ofelectrical stimulation which may be a function of amplitude, pulsewidth, and pulse rate. The particular electrodes and stimulationintensity levels that are selected in accordance with examples of thisdisclosure may spatially characterize an oscillation source and alsoserve, directly or indirectly, as parameters for delivery of electricalstimulation therapy. Hence, in such an example, sensed signals andintensities selected to define the therapy parameters also may berepresentative of a therapy target that is a function of a spatialextent of an oscillatory source. In other examples, the therapy targetmay be defined and then the parameters may be selected based on thetherapy target definition.

During a trial stage in which IMD 110 is evaluated to determine whetherIMD 110 provides efficacious therapy to patient 104, a plurality oftherapy target definition programs and/or therapy programs may be testedand evaluated for efficacy. Therapy target definition programs and/ortherapy programs may be selected for storage within IMD 110 based on theresults of the trial stage.

During chronic therapy in which IMD 110 is implanted within patient 104for delivery of therapy on a non-temporary basis, IMD 110 may generateand deliver stimulation signals to patient 104 according to differenttherapy target definition programs and/or therapy programs. In addition,in some examples, patient 104 may modify the value of one or moretherapy parameter values within a single given program or switch betweenprograms in order to alter the efficacy of the therapy as perceived bypatient 104 with the aid of programmer 120. The memory of IMD 110 maystore instructions defining the extent to which patient 104 may adjusttherapy parameters, switch between programs, or undertake other therapyadjustments. Patient 104 may generate additional programs for use by IMD110 via external programmer 120 at any time during therapy or asdesignated by the clinician.

External programmer 120 may wirelessly communicate with IMD 110 asneeded to provide or retrieve therapy information. Programmer 120 may bean external computing device that the user, e.g., the clinician and/orpatient 104, may use to communicate with IMD 110. For example,programmer 120 may be a clinician programmer that the clinician uses tocommunicate with IMD 110 and program one or more target definitionprograms and/or one or more therapy programs for IMD 110. Alternatively,programmer 120 may be a patient programmer that allows patient 104 toselect programs and/or view and modify therapy parameters. The clinicianprogrammer may include more programming features than the patientprogrammer. In other words, more complex or sensitive tasks may only beallowed by the clinician programmer to prevent an untrained patient frommaking undesirable changes to IMD 110.

Programmer 120 may be a hand-held computing device with a displayviewable by the user and an interface for providing input to programmer120 (i.e., a user input mechanism). For example, programmer 120 mayinclude a small display screen (e.g., a liquid crystal display (LCD) ora light emitting diode (LED) display) that presents information to theuser. In addition, programmer 120 may include a touch screen display,keypad, buttons, a peripheral pointing device or another input mechanismthat allows the user to navigate though the user interface of programmer120 and provide input. If programmer 120 includes buttons and a keypad,the buttons may be dedicated to performing a certain function, i.e., apower button, or the buttons and the keypad may be soft keys that changein function depending upon the section of the user interface currentlyviewed by the user. Alternatively, a screen of programmer 120 may be atouch screen that allows the user to provide input directly to the userinterface shown on the display. The user may use a stylus or a finger toprovide input to the display.

In other examples, programmer 120 may be a larger workstation or aseparate application within another multi-function device, rather than adedicated computing device. For example, the multi-function device maybe a notebook computer, tablet computer, workstation, cellular phone,personal digital assistant or another computing device that may run anapplication that enables the computing device to operate as medicaldevice programmer 120. A wireless adapter coupled to the computingdevice may enable secure communication between the computing device andIMD 110 or a hardwired connection may be provided.

When programmer 120 is configured for use by the clinician, programmer120 may be used to transmit initial programming information to IMD 110.This initial information may include hardware information, such as thetype of lead 114 and the electrode arrangement, the position of lead 114within brain 106, the configuration of electrodes 118, initial programsdefining therapy target definition programs and/or therapy programs tobe implemented based on therapy target definitions, and any otherinformation the clinician desires to program into IMD 110. Programmer120 may also be capable of completing functional tests (e.g., measuringthe impedance of electrodes 118 a, 118 b, 118 c, and 118 d).

The clinician may also store therapy target definition programs and/ortherapy programs within IMD 110 with the aid of programmer 120. During aprogramming session, the clinician may determine one or more targettherapy definition programs and/or therapy programs that may provideefficacious therapy to patient 104 to address symptoms associated withthe patient condition, and, in some cases, specific to one or moredifferent patient states, such as a sleep state, movement state or reststate. During the programming session, patient 104 may provide feedbackto the clinician as to the efficacy of the specific program beingevaluated or the clinician may evaluate the efficacy based on one ormore physiological parameters of patient 104 (e.g., signals sensed fromthe brain, muscle activity or muscle tone). Programmer 120 may assistthe clinician in the creation/identification of target therapydefinition programs and/or therapy programs by providing a methodicalsystem for identifying potentially beneficial therapy target definitionprograms and/or therapy programs, including programs including therapyparameters based on a therapy target definition.

Programmer 120 may also be configured for use by patient 104. Whenconfigured as a patient programmer, programmer 120 may have limitedfunctionality (compared to a clinician programmer) in order to preventpatient 104 from altering critical functions of IMD 110 or applicationsthat may be detrimental to patient 104. In this manner, programmer 120may only allow patient 104 to adjust values for certain therapyparameters or set an available range of values for a particular therapyparameter.

Programmer 120 may also provide an indication to patient 104 whentherapy is being delivered, when patient input has triggered a change intherapy or when the power source within programmer 120 or IMD 110 needsto be replaced or recharged. For example, programmer 120 may include analert LED, may flash a message to patient 104 via a programmer display,generate an audible sound or somatosensory cue to confirm patient inputwas received, e.g., to indicate a patient state or to manually modify atherapy parameter.

Programmer 120 may be configured to communicate to IMD 110 and,optionally, another computing device, via wireless communication.Programmer 120, for example, may communicate via wireless communicationwith IMD 110 using radio frequency (RF) or inductive telemetrytechniques according to any proprietary or industry standardcommunication protocols known in the art. Programmer 120 may alsocommunicate with another programmer or computing device via a wired orwireless connection using any of a variety of local wirelesscommunication techniques, such as RF communication according to the802.11 or Bluetooth specification sets, infrared (IR) communicationaccording to the IRDA specification set, or other standard orproprietary telemetry protocols. Programmer 120 may also communicatewith other programming or computing devices via exchange of removablemedia, such as magnetic or optical disks, memory cards or memory sticks.Further, programmer 120 may communicate with IMD 110 and anotherprogrammer via remote telemetry techniques known in the art,communicating via a local area network (LAN), wide area network (WAN),public switched telephone network (PSTN), or cellular telephone network,for example.

Therapy system 102 may be implemented to provide chronic stimulationtherapy to patient 104 over the course of several months or years.However, system 102 may also be employed on a trial basis to evaluatetherapy before committing to full implantation. If implementedtemporarily, some components of system 102 may not be implanted withinpatient 104. For example, patient 104 may be fitted with an externalmedical device, such as a trial stimulator, rather than IMD 110. Theexternal medical device may be coupled to percutaneous leads or toimplanted leads via a percutaneous extension. If the trial stimulatorindicates DBS system 102 provides effective treatment to patient 104,the clinician may implant a chronic stimulator within patient 104 forrelatively long-term treatment. As another example, an external medicaldevice may be used in combination with lead 114 to define a therapytarget and deliver therapy in a single procedure without long-termtreatment. For example, lead 114 may be implanted within brain 106 ofpatient 104 using, for example a motor 122, as shown in FIG. 1A, andsystem 102 may be used to define a therapy target and deliver therapy inthe form of a lesion corresponding to the therapy target definition, andlead 114 may be removed from brain 106 of patient 104.

FIG. 2 is a functional block diagram illustrating components of anexample IMD 110. In the example shown in FIG. 2, IMD 110 includescontroller 202, memory 214, electrical stimulation circuitry 204,sensing circuitry 206, switch module 208, telemetry module 210, andpower source 212. Memory 214 may include any volatile or non-volatilemedia, such as a random access memory (RAM), read only memory (ROM),non-volatile RAM (NVRAM), electrically erasable programmable ROM(EEPROM), flash memory, and the like. Memory 214 may storecomputer-readable instructions that, when executed by controller 202,cause IMD 110 to perform various functions.

Memory 214 may store therapy target definition programs for defining atherapy target as described with reference to FIGS. 4A-10, and/ortherapy programs for delivering therapy based on therapy targetdefinitions. Memory 214 may store programs in separate memories withinmemory 214 or separate areas within memory 214. In addition, in someexamples, memory 214 may store a bioelectrical brain signal sensed viaat least some of the stored sense electrode combinations and/or one ormore frequency band characteristics of the bioelectrical brain signals.Each stored therapy program defines a particular set of electricalstimulation parameters (also referred to as therapy parameters) such asa stimulation electrode combination, electrode polarity, current orvoltage amplitude, pulse width, whether cycling is on/off, waveformshape, and pulse rate to be applied based on a therapy targetdefinition. In some examples, individual therapy programs may be storedas a therapy group, which defines a set of therapy programs with whichstimulation may be generated. The stimulation signals defined by thetherapy programs of the therapy group may be delivered together on anoverlapping or non-overlapping (e.g., time-interleaved) basis.

Memory 214 may store sense and stimulation electrode combinations thatidentify sense electrode combinations and associated stimulationelectrode combinations. As described above, in some examples, the senseand stimulation electrode combinations may include the same subset ofelectrodes or may include different subsets of electrodes. Thus, memory214 can store a plurality of sense electrode combinations and, for eachsense electrode combination, store information identifying thestimulation electrode combination that is associated with the respectivesense electrode combination. The associations between sense andstimulation electrode combinations can be determined, e.g., by aclinician or automatically by controller 202.

In some examples, corresponding sense and stimulation electrodecombinations may comprise some or all of the same electrodes. In otherexamples, however, some or all of the electrodes in corresponding senseand stimulation electrode combinations may be different. For example, astimulation electrode combination may include more electrodes than thecorresponding sense electrode combination in order to increase theefficacy of the stimulation therapy. In some examples, as discussedabove, stimulation may be delivered via a stimulation electrodecombination to a tissue site that is different than the tissue siteclosest to the corresponding sense electrode combination but is withinthe same region, e.g., the thalamus, of brain 106 in order to mitigateany irregular oscillations or other irregular brain activity within thetissue site associated with the sense electrode combination.

Memory 214 may store operating instructions to guide general operationof IMD 110 under control of controller 202, and may include instructionsfor measuring the impedance of electrodes 118 and/or determining thedistance between electrodes 118.

Electrical stimulation circuitry 204, under the control of controller202, may generate stimulation signals for delivery to patient 104 viaselected combinations of electrodes 118. As described in further detailwith respect to FIGS. 4A-10, electrical stimulation circuitry 204 maygenerate stimulation signals for delivery to patient 104 to define atherapy target. In some examples, electrical stimulation circuitry 204may also generate stimulation signals for delivery to patient to delivertherapy based on the therapy target definition.

Controller 202 may include any one or more of a microprocessor, acontroller, a digital signal processor (DSP), an application specificintegrated circuit (ASIC), a field-programmable gate array (FPGA),discrete logic circuitry, and the functions attributed to controller 202herein may be embodied as firmware, hardware, software or anycombination thereof. Controller 202 may control electrical stimulationcircuitry 204 according to therapy target definition programs stored inmemory 214, and/or according to therapy programs stored in memory 214and a therapy target definition and/or defined parameters (which may berepresentative of the therapy target definition or derived from thetherapy target definition), to apply particular stimulation parametervalues specified by one or more of programs, such as amplitude, pulsewidth, and pulse rate.

In the example shown in FIG. 2, the set of electrodes 118 includeselectrodes 118 a, 118 b, 118 c, and 118 d. Controller 202 also controlsswitch module 208 to apply the stimulation signals generated byelectrical stimulation circuitry 404 to selected combinations ofelectrodes 118. In particular, switch module 208 may couple stimulationsignals to selected conductors within lead 114, which, in turn, deliverthe stimulation signals across selected electrodes 118. Switch module208 may be a switch array, switch matrix, multiplexer, or any other typeof switching module configured to selectively couple stimulation energyto selected electrodes 118 and to selectively sense bioelectrical brainsignals with selected electrodes 118. Hence, electrical stimulationcircuitry 204 is coupled to electrodes 118 via switch module 208 andconductors within lead 114. In some examples, however, IMD 110 does notinclude switch module 208. Instead, IMD 110 may include a dedicatedvoltage or current source for electrical stimulation circuitry and asink for each electrode. Controller 202 may control the source and sinksto apply the electrical stimulation signals generated by electricalstimulation circuitry 202 to selected combinations of electrodes 118.

Electrical stimulation circuitry 204 may be a single channel ormulti-channel electrical stimulation circuitry. In particular,electrical stimulation circuitry 204 may be capable of delivering asingle stimulation pulse, multiple stimulation pulses, or a continuoussignal at a given time via a single electrode combination or multiplestimulation pulses at a given time via multiple electrode combinations.In some examples, however, electrical stimulation circuitry 204 andswitch module 208 may be configured to deliver multiple channels on atime-interleaved basis. For example, switch module 208 may serve to timedivide the output of electrical stimulation circuitry 204 acrossdifferent electrode combinations at different times to deliver multipleprograms or channels of stimulation energy to patient 104.

Sensing circuitry 206, under the control of controller 202, may sensebioelectrical brain signals and provide the sensed bioelectrical brainsignals to controller 202. Controller 202 may control switch module 208to couple sensing circuitry 206 to a selected combinations of electrodes118, i.e., a sense electrode combination. In this way, IMD 110 isconfigured such that sensing circuitry 206 may sense bioelectrical brainsignals with a plurality of different sense electrode combinations.Switch module 208 may be electrically coupled to the selected electrodes118 via the conductors within lead 114, which, in turn, deliver thebioelectrical brain signal sensed across the selected electrodes 118 tosensing circuitry 206. The bioelectrical brain signal may includeelectrical signals that are indicative of electrical activity withinbrain 106 of patient 104.

Although sensing circuitry 206 is incorporated into a common housingwith electrical stimulation circuitry 204 and controller 202 in FIG. 2,in other examples, sensing circuitry 206 may be in a separate housingfrom IMD 110 and may communicate with controller 202 via wired orwireless communication techniques. Example bioelectrical brain signalsinclude, but are not limited to, a signal generated from local fieldpotentials within one or more regions of brain 104. EEG and ECoG signalsare examples of local field potentials that may be measured within brain104. However, local field potentials may include a broader genus ofelectrical signals within brain 106 of patient 104. Controller 202 mayanalyze a plurality of bioelectrical brain signals, e.g., by determiningrelative values of signal characteristics (e.g., potentials or frequencydomain characteristics) of the biosignal. Beta band signals and/or gammaband signals may also be measured within brain 104 and may result, forexample, from a source of beta and/or gamma oscillations, such as source108, within brain 106.

Telemetry module 210 supports wireless communication between IMD 110 andan external programmer 120 or another computing device under the controlof controller 202. Controller 202 of IMD 110 may receive, updates totherapy definition programs and/or updates to therapy programs, fromprogrammer 120 via telemetry module 210. The updates to the therapyprograms may be stored within memory 214. Telemetry module 210 may sendinformation related to a therapy target definition to programmer 120 viatelemetry module 210. For example, telemetry module 210 may send aninitial therapy target definition to programmer 120. Telemetry module210 may also send an updated therapy target definition to programmer 120to indicate changes to source 108 and/or movement of lead 114 withrespect to source 108. Telemetry module 210 in IMD 110, as well astelemetry modules in other devices and systems described herein, such asprogrammer 120, may accomplish communication by radiofrequency (RF)communication techniques. In addition, telemetry module 210 maycommunicate with external medical device programmer 120 via proximalinductive interaction of IMD 110 with programmer 120. Accordingly,telemetry module 210 may send information to external programmer 120 ona continuous basis, at periodic intervals, or upon request from IMD 110or programmer 120.

In some examples, IMD 110 and/or programmer 120 may define a therapytarget and/or select therapy parameters based on the therapy targetdefinition. For example, IMD 110 may define the therapy target andselect therapy parameters based on the therapy target definition. Inother examples, IMD 110 may define the therapy target and send thetherapy target definition to programmer 120 and programmer 120 mayselect therapy parameters based on the therapy target definition andsend the selected therapy parameters to IMD 110. In some examples, IMD110 may deliver and/or sense signals and send information indicative ofthe delivered and/or sensed signals to programmer 120 and programmer 120may define the therapy target, select therapy parameters based on thetherapy target definition, and send the selected therapy parameters toIMD 110. In some examples, IMD 110 may deliver and/or sense signals andsend information indicative of the delivered and/or sensed signals toprogrammer 120, programmer 120 may define the therapy target and sendthe therapy target definition to IMD 110, and IMD 110 may select therapyparameters based on the therapy target definition. One or more modulesfor defining a therapy target and/or selecting therapy parameters basedon the therapy target definition may be stored and/or executed by one ormore of IMD 110, programmer 120, and/or any other suitable component. Insome examples, a user may select one or more therapy parameters based ona therapy target definition.

In some examples, selecting therapy parameters based on definedparameters may comprise selecting the defined parameters. In otherexamples, selecting therapy parameters based on defined parameters mayinclude selecting parameters that are a function of the definedparameters but are not the same as the defined parameters. For example,defining the therapy target may comprise defining parameters fordelivering therapy, including, for example, selecting electrodes fordelivery of electrical stimulation and/or selecting intensities ofelectrical stimulation delivered by the selected electrodes. Theselected electrodes and selected intensities may define the therapytarget and directly form parameters for delivery of electricalstimulation therapy. In other examples, the therapy target may bedefined and then the stimulation parameters may be selected based on thetherapy target definition.

Power source 212 may deliver operating power to various components ofIMD 110. Power source 212 may include a small rechargeable ornon-rechargeable battery and a power generation circuit to produce theoperating power. Recharging may be accomplished through proximalinductive interaction between an external charger and an inductivecharging coil within IMD 110. In some examples, power requirements maybe small enough to allow IMD 110 to utilize patient motion and implementa kinetic energy-scavenging device to trickle charge a rechargeablebattery. In other examples, traditional batteries may be used for alimited period of time.

FIG. 3 is a functional block diagram illustrating components of anexample medical device programmer 120, which includes controller 302,memory 310, telemetry module 306, user interface 304, and power source308. Controller 302 controls user interface 304 and telemetry module306, and stores and retrieves information and instructions to and frommemory 310. Programmer 120 may be configured for use as a clinicianprogrammer or a patient programmer. Controller 302 may comprise anycombination of one or more processors including one or moremicroprocessors, DSPs, ASICs, FPGAs, or other equivalent integrated ordiscrete logic circuitry. Accordingly, controller 302 may include anysuitable structure, whether in hardware, software, firmware, or anycombination thereof, to perform the functions ascribed herein tocontroller 302.

A user, such as a clinician or patient 104, may interact with programmer120 through user interface 304. User interface 304 may include adisplay, such as a LCD or LED display or other type of screen, topresent information related to a therapy target definition and/or atherapy, such as an image depicting a 3-dimensional representation ofthe spatial extent (e.g., size and/or shape) of source 108 based on atherapy target defined by system 102. In addition, user interface 304may include an input mechanism to receive input from the user. The inputmechanisms may include, for example, buttons, a keypad (e.g., analphanumeric keypad), a peripheral pointing device or another inputmechanism that allows the user to navigate though user interfacespresented by controller 302 of programmer 120 and provide input.

If programmer 120 includes buttons and a keypad, the buttons may bededicated to performing a certain function, i.e., a power button, or thebuttons and the keypad may be soft keys that change in functiondepending upon the section of the user interface currently viewed by theuser. Alternatively, a screen of programmer 120 may be a touch screenthat allows the user to provide input directly to the user interfaceshown on the display. The user may use a stylus or a finger to provideinput to the display. In other examples, user interface 304 alsoincludes audio circuitry for providing audible instructions or sounds topatient 104 and/or receiving voice commands from patient 104, which maybe useful if patient 104 has limited motor functions. Patient 104, aclinician or another user may also interact with programmer 120 tomanually select therapy programs, generate new therapy programs, modifytherapy programs through individual or global adjustments, and transmitthe new programs to IMD 110. For example, although therapy programs maybe based on a therapy target definition, patient 104 may have the optionto choose between different programs based on the therapy targetdefinition and/or make adjustments to programs.

In some examples, at least some of the control of therapy delivery byIMD 110 may be implemented by controller 302 of programmer 120. Forexample, in some examples, controller 302 may control delivery ofstimulation signals by IMD 110 and receive bioelectrical brain signals,in response to the delivered signals, from IMD 110 or from a sensingcircuitry that is separate from IMD 110. The separate sensing circuitrymay, but need not be, implanted within patient 110. In some examples,controller 302 may define a therapy target based on the receivedsignals, e.g., by implementing an algorithm similar or identical to thatimplemented by IMD 110 and stored by memory 211 of IMD 110 and describedwith reference to FIGS. 4A-10. Controller 202 of IMD 110 may receive thesignal from programmer 120 via its respective telemetry module 210 (FIG.2).

Memory 310 may include instructions for operating user interface 304 andtelemetry module 306, and for managing power source 308. Memory 310 mayalso store any therapy data retrieved from IMD 110 during the course oftherapy. The clinician may use this therapy data to determine theprogression of the patient condition in order to predict futuretreatment. Memory 310 may include any volatile or nonvolatile memory,such as RAM, ROM, EEPROM or flash memory. Memory 310 may also include aremovable memory portion that may be used to provide memory updates orincreases in memory capacities. A removable memory may also allowsensitive patient data to be removed before programmer 120 is used by adifferent patient.

Wireless telemetry in programmer 120 may be accomplished by RFcommunication or proximal inductive interaction of external programmer120 with IMD 110. This wireless communication is possible through theuse of telemetry module 306, which may communicate with a proprietaryprotocol or industry-standard protocol such as using the Bluetoothspecification set. Accordingly, telemetry module 306 may be similar tothe telemetry module contained within IMD 110. In alternative examples,programmer 120 may be capable of infrared communication or directcommunication through a wired connection. In this manner, other externaldevices may be capable of communicating with programmer 120 withoutneeding to establish a secure wireless connection.

Power source 308 may deliver operating power to the components ofprogrammer 120. Power source 308 may include a battery and a powergeneration circuit to produce the operating power. In some examples, thebattery may be rechargeable to allow extended operation. Recharging maybe accomplished by electrically coupling power source 308 to a cradle orplug that is connected to an alternating current (AC) outlet. Inaddition, recharging may be accomplished through proximal inductiveinteraction between an external charger and an inductive charging coilwithin programmer 120. In other examples, traditional batteries (e.g.,nickel cadmium or lithium ion batteries) may be used. In addition,programmer 120 may be directly coupled to an alternating current outletto operate. Power source 308 may include circuitry to monitor powerremaining within a battery. In this manner, user interface 304 mayprovide a current battery level indicator or low battery level indicatorwhen the battery needs to be replaced or recharged. In some cases, powersource 308 may be capable of estimating the remaining time of operationusing the current battery.

FIGS. 4A and 4B are conceptual diagrams illustrating exampleconfigurations for sensing electrical signals at a plurality ofdifferent positions within brain 106 of patient 104.

As shown in FIG. 4A, lead 114 with electrodes, 118 a, 118 b, 118 c, and118 d of lead 114 may be positioned within brain 106 adjacent totriangular source 108, as also illustrated in FIGS. 1A and 1B. Source108 may be considered triangular in the sense that at least across-section of source 108 extending in a radial direction away fromlead 114 may be substantially triangular in shape. Conventionaltechniques for measuring source 108 may not readily be able to determinesuch a shape for source 108 and/or distinguish between different shapesof sources. Each of electrodes 118 a, 118 b, 118 c, and 118 d may senselocal field potentials at a plurality of different positions withinbrain 106, corresponding to the positions of each of electrodes 118 a,118 b, 118 c, and 118 d before electrical stimulation is delivered.Although each of electrodes 118 a and 118 b are described as singleelectrodes, electrodes 118 a and 118 b may each correspond to a group ofelectrodes, each group corresponding to a position within brain 106. EEGand ECoG signals are examples of local field potentials that may bemeasured within brain 104. However, local field potentials may include abroader genus of electrical signals within brain 106 of patient 104. Inthe example of FIG. 4A, triangular source 108 has a thickness of 1 mm, aheight of 6 mm, and a width of 4 mm.

As shown in FIG. 4B, lead 114 with electrodes, 118 a, 118 b, 118 c, and118 d of lead 114 may be positioned within brain 106 adjacent tospherical source 408. Source 408 may be considered spherical in thesense that at least a cross-section of source 408 extending in a radialdirection away from lead 114 may be substantially circular in shape.Conventional techniques for measuring source 108 may not readily be ableto determine such a shape for source 408 and/or distinguish betweendifferent shapes of sources. Each of electrodes 118 a, 118 b, 118 c, and118 d may sense local field potentials at a plurality of differentpositions within brain 106, corresponding to the positions of each ofelectrodes 118 a, 118 b, 118 c, and 118 d at a time at which electricalstimulation is not delivered. In the example of FIG. 4B, sphericalsource 408 has a thickness of 0.5 mm.

As shown in each of FIGS. 4A and 4B, electrical signals may be sensed ata plurality of different positions when electrical stimulation is notdelivered. For example, sensing circuitry 206 may sense electricalsignals at positions corresponding to each of electrodes, electrodegroups, or electrode segments 118 a, 118 b, 118 c, 118 d along thelength of lead 114. In some examples, the sensing may be performed inbipolar fashion such that the sensed local field potentials are measuredas a comparison to a reference local field potential such that thereference local field potential is designated as having a value of zeroand the values of the sensed local field potentials are based on thedeviation from the reference. The reference local field potential maybe, for example, a local field potential measured at a position notaffected by source 108 and the sensed local field potentials may bemeasured as a deviation from that reference local field potential. Thereference local field potential may be that measured at any suitableposition. As shown in FIGS. 4A and 4B, a reference local field potentialmay be designated as 0 V and the other local field potentials may bemeasured with reference to the reference local field potential. In theillustrated example, a position closest to source 108 may be expected tohave the greatest deviation from the reference.

The local field potential may be characterized by the magnitude oramplitude of the sensed signal. Alternatively, the local field potentialmay be characterized by the spectral power within a specific frequencyband (e.g., beta band).

FIG. 5 is a graph illustrating electrical signals sensed at theplurality of different positions within a brain of a patient for each oftriangular source 108, shown in FIG. 4A, spherical source 408, shown inFIG. 4B, and a point source (not shown).

In some examples, the sensed local field potentials, as described withreference to FIGS. 4A and 4B, may be normalized based on the positionwith the sensed local field potential with the greatest deviation fromthe reference. For example, in the illustrated example, for thetriangular source illustrated in FIG. 4A, the position associated with118 a may be associated with the local field potential with the greatestdeviation from the reference such that it is normalized as “1.0.” Theposition associated with 118 b may be associated with the local fieldpotential with a deviation from the reference that is approximately 0.9of that of the position associated with 118 a, such that it isnormalized to “0.9.” Likewise, the sensed local field potentials atpositions corresponding to 118 c and 118 d may have a deviation from thereference that is approximately 0.7 and 0.5 of that of the positionassociated with 118 a, and may thus be normalized to be approximately“0.7” and “0.5.”

Examples of normalized local field potentials for each of a sphericaland point source are also shown in the graph of FIG. 5.

As shown in FIG. 5, the profile of normalized local field potentialssensed at each of electrodes 118 a, 118 b, 118 c, and 118 d aresubstantially similar adjacent to each of the differently shapedsources.

Because the profile of normalized local field potentials sensed at eachof electrodes 118 a, 118 b, 118 c, and 118 d may be substantiallysimilar adjacent to each of the differently shaped sources, asillustrated with reference to FIGS. 4A, 4B, and 5, sensing these localfield potentials alone may not allow for distinguishing the shapes ofthe different sources and additional information may be needed toidentify a shape for a particular source and/or therapy parametersappropriate for a particular source shape. Characteristics of localfield potentials between pairs of electrodes (e.g., electrode pairs 118a-118 b or 118 b-118 c) may also be similar indicating that additionalinformation may be needed to characterize the position and spatialextent of the source. More than one local field potential characteristicmay be used to characterize the source (e.g., ratio of the power in twodifferent frequency bands).

In some examples, the positions at which the sensed local fieldpotentials are over a threshold amount or are the highest when comparedto other positions, for example, the positions corresponding to 118 aand 118 b for each of the example triangular source, spherical source,and point source, may be of particular interest for additional analysisas the local field potentials may indicate that positions correspondingto each of electrodes 118 a and 118 b may be adjacent to the source. Insome examples, the positions with the highest sensed local fieldpotentials may be selected for additional analysis. In other examples,each of the positions may be selected for additional analysis. Forexample, obtaining the local field potential power profiles as shown mayallow controller 202 and/or controller 302 to select those electrodeswith the highest sensed power for further analysis.

FIGS. 6A, 6B, and 6C are diagrams illustrating example electrodeconfigurations for delivering electrical stimulation at a plurality ofdifferent intensities at each of a plurality of different positionswithin brain 106 of patient 104 and sensing electrical signals at eachof the different positions in response to the electrical stimulationdelivered at each of the different intensities. Electrodeconfigurations, such as those shown in FIGS. 6A, 6B and 6C, may permitspatial definition of a therapy target based on spatial characteristicsof a source of signals within a brain of the patient.

FIG. 6A illustrates an example including lead 114 with electrodes 118adjacent to triangular source 108. As described with reference to FIGS.4A and 5, local field potentials may be sensed at each of the positionscorresponding to electrodes 118 a, 118 b, 118 c, and 118 d, which mayeach correspond to an axial position along lead 114. In some exampleswhere electrodes 118 are segmented electrodes, segments of electrodes118 may also correspond to circumferential positions about lead 114, asdiscussed in further detail below. The sensed local field potentials maybe normalized based on the highest local field potential. For example,the normalized local field potential for each of positions correspondingto 118 a, 118 b, 118 c, and 118 d may be 1.0, 0.9, 0.7, and 0.5,respectively.

Controller 202 and/or controller 302 may control electrical stimulationcircuitry 204 to deliver electrical stimulation at the positionscorresponding to each of electrodes 118 a, 118 b, 118 c, and 118 d. Forexample, controller 202 and/or controller 302 may control electricalstimulation circuitry 204 to deliver electrical stimulation viaelectrode 118 a, 118 b, 118 c, and 118 d. In other examples, electricalstimulation may be delivered to less that each electrode 118 based onthe local field potentials sensed at the corresponding positions. Forexample, if a sensed local field potential was particularly low at agiven position, such that it was under a threshold amount, electricalstimulation may not be delivered at that position.

Sensing circuitry 206 may sense electrical signals at each of thedifferent positions within brain 106 of patient 104 in response to theelectrical stimulation. For example, electrical signals may be sensed byeach of electrodes 118 a, 118 b, 118 c, and 118 d. As previouslydescribed, although each of electrodes 118 a and 118 b are described assingle electrodes, either or both of electrodes 118 a and 118 b maycorrespond to a group of electrodes, an electrode segment, or a group ofelectrode segments, each corresponding to a position within brain 106.The same or different electrodes within a group of electrodes 118 a and118 b may be used for delivering electrical stimulation and/or sensingelectrical signals at each of the corresponding positions.

At each selected position, corresponding to each of electrodes 118 a,118 b, 118 c, and 118 d, electrical stimulation may be delivered at aplurality of different intensities and electrical signals may be sensedin response to the electrical stimulation delivered at each of thedifferent intensities. For example, sensing circuitry 206 may beconfigured to sense beta band signals at each of the selected positions.The stimulation at different intensities may be delivered as stimulationat progressively increasing intensity levels, e.g., as a function ofincreasing amplitude, pulse width and/or pulse width. Electricalstimulation circuitry 204 may deliver electrical stimulation at a firstintensity and sensing circuitry 206 may sense first beta band signals inresponse to the electrical stimulation at the first intensity.Electrical stimulation circuitry 204 may deliver electrical stimulationat a second intensity that is higher than the first intensity andsensing circuitry 206 may sense second beta band signals in response tothe electrical stimulation at the second intensity. In response to theincreased intensity of the electrical stimulation, the second sensedbeta band signals may be lower than the first sensed beta band signals,as the increased intensity may be effective in further suppressing thebeta band oscillation emitted by the source.

Electrical stimulation circuitry 204 may deliver electrical stimulationat increasing intensities until the sensed beta band signals aresubstantially suppressed. The level of the signal that is sensed may bespectral power of the local field potential. In some examples, the levelmay be of any suitable characteristic of the local field potentialoscillation.

In some examples, electrical stimulation circuitry 204 may deliverelectrical stimulation at a variety of intensities, sensing circuitry206 may sense beta band signals in response to each of the deliveredelectrical stimulation intensities, and controller 202 and/or controller302 may determine the responsiveness of the sensed beta band signal tothe delivered electrical stimulation.

Based on the normalized local field potentials, controller 202 and/orcontroller 302 may determine a sequence for delivering electricalstimulation and sensing electrical signals in response to the deliveredelectrical stimulation at each of the positions corresponding toelectrodes 118 a, 118 b, 118 c, 118 d. For example, controller 202and/or controller 302 may determine a sequence from the position withthe greatest normalized local field potential to the position with thelowest normalized local field potential. For example, the sequence maybe 118 a, 118 b, 118 c, and 118 d based on the descending normalizedlocal field potentials corresponding to those positions of 1.0, 0.9,0.7, and 0.5, respectively. In other examples, a different sequence maybe determined. In some examples, the sequence may include fewer than allof the positions corresponding to each of electrodes 118 a, 118 b, 118c, and 118 d. For example, a local field potential and/or the normalizedlocal field potential corresponding to one or more of the positions maybe under a threshold amount such that it may be determined to not be ofinterest for further analysis. For example, a local field potential thatis particularly small in comparison with the other positions may bedetermined to be too far from source 108 to be of interest.

For example, in the illustrated example, controller 202 and/orcontroller 302 may start by delivering electrical stimulation andsensing beta band signals in response to the delivered electricalstimulation at the position associated with 118 a.

For example, controller 202 and/or controller 302 may control electricalstimulation circuitry 204 to deliver electrical stimulation at aplurality of increasing intensities and may sense beta band signals inresponse to the delivered electrical stimulation to determine thechanges to the beta band signals in response to the delivered electricalstimulation.

Sensing circuitry 206 may sense a beta band signal at the positioncorresponding to 118 a before electrical stimulation is delivered. Thesensed beta band signal may be, for example, 10 μV. Controller 202and/or controller 302 may control electrical stimulation circuitry 204to deliver a first electrical stimulation at the position correspondingto electrode 118 a at a first intensity of 0.5 V or 0.5 milliamp.Sensing circuitry 206 may sense the beta band signal at the position inresponse to the delivered electrical stimulation. The sensed beta bandsignal may be, for example, 9.5 μV.

At the position corresponding to electrode 118 a, controller 202 and/orcontroller 302 may deliver electrical stimulation at increasingintensities, each time increasing the intensity, by, for example, 0.5 Vor 0.5 milliamp, and sensing circuitry 206 may sense the beta bandsignal in response to the delivered electrical stimulation. Based on thesensed beta band signals in response to the increasing intensities ofdelivered electrical stimulation, controller 202 and/or controller 302may determine the responsiveness of the beta band signal to theelectrical stimulation. For example, controller 202 and/or controller302 may continue to deliver electrical stimulation at intensitiesincreasing by, for example, 0.5 V or 0.5 milliamp, until increasing theintensity no longer results in a lower beta band signal. For example, inthe example described above, controller 202 and/or controller 302 maydeliver electrical stimulation at 0.5V or 0.5 milliamp, 1.0 V or 1.0milliamp, 1.5 V or 1.5 milliamps, etc., at increasing intervals of 0.5 Vor 0.5 milliamp, up to 10 V or 10 milliamps, and the sensed beta bandsignal may decrease in response to each increase in intensity. Whenelectrical stimulation is delivered at 10 V or 10 milliamps, the sensedbeta band signal in response to the electrical stimulation may be, forexample, 2 μV. Controller 202 and/or controller 302 may then increasethe intensity again, to 10.5 V or 10.5 milliamps. This time, the sensedbeta band signal that results may not decrease but may remain at 2 μV.Controller 202 and/or controller 302 may increase the intensity again,to 11 V or 11 milliamps. The resulting beta band signal may, again,remain at 2 μV. Because increasing the intensity of electricalstimulation to 10 V or 10 milliamps decreases the resulting beta bandsignal but increasing the intensity of electrical stimulation over 10 Vor 10 milliamps does not result in a decrease in the resulting beta bandsignal, 10 V or 10 milliamps may be determined to be the intensity ofelectrical stimulation that maximally suppresses the beta band signal atthe position corresponding to electrode 118 a because additionalincreases in intensity above 10 V or 10 milliamps does not result infurther suppression of the beta band signal. In this example, themaximally suppressive intensity of stimulation is the intensity at whichadditional increases in intensity do not further suppress the beta bandsignals. In other examples, the maximally suppressive intensity may bethe intensity of stimulation that suppresses the beta band signal to beunder a threshold amount or that suppresses the beta band signal by athreshold amount.

Any combination of suitable factors or processes may be used todetermine the intensity of electrical stimulation that maximallysuppresses a beta band signal at a particular position. For example, asdescribed above, the intensity of electrical stimulation may beincreased at any suitable interval, for example by 0.5 V or 0.5milliamp, and the resulting beta band signal may be sensed. Theintensity of electrical stimulation may be increased as long as theresulting beta band decreases. In some examples, as described above, ifan increase in intensity, for example from 10V or 10 milliamps to 10.5or 10.5 milliamps, does not decrease the resulting beta band signal, theintensity may be increased again, for example, to 11.0 V or 11.0milliamps, and the resulting beta band signal sensed to determinewhether any decrease results. This increase in intensity following anincrease that results in no decrease in the beta band signal may berepeated, for example, two or three times, to determine that an increasein intensity over 10 V or 10 milliamps does not result in a decrease inthe beta band signal. Based on this determination, 10V or 10 milliampsmay be determined to be the intensity that maximally suppresses the betaband signal for that position.

As another example, intensity of electrical stimulation may be increaseduntil patient 104 exhibits improvement in symptoms that may indicateoptimal suppression of the beta band signal. For example, intensity ofdelivered electrical stimulation may be increased at regular intervalsuntil, in the case of patient 106 having Parkinson's disease, patient106 is able to, for example, increase speed of intentional movement to adesired or optimal speed. For example, electrical stimulation may bedelivered at increasing intensity until a desired patient response isreached and/or until a patient response is optimized such thatadditional increases in intensity do not result in an improved patientresponse. Desired patient responses may include, for example, increasedspeed of intentional movement, decrease in tremor or pain, improvedsensory activities or acuity, reduced bradykinesia, improved sleep orother benefits. Such results may be monitored with diagnostic toolsand/or manually, such as visually, by a clinician. Patient responses toincremental changes in stimulation intensity may also be monitored andused for defining the therapy target. For instance, scores assigned by aclinical observer according to a standardized rating scale such as theUnified Parkinson's Disease Rating Scale (UPDRS) based on patientevaluation and patient responses may in some examples be used fordefining the therapy target.

In some examples, increases in intensity may be stopped if adverse sideeffects are observed or if no further suppression is achieved. Forexample, in the example described above, intensity of electricalstimulation may be increased at intervals of 0.5 V or 0.5 milliamp aslong as the resulting beta band signal decreases and until adversesymptoms are observed. For example, decreases in the beta band signalmay result for each increase in stimulation intensity from 0.5 V or 0.5milliamp to 1.0 V or 1.0 milliamp, then from 1.0 V or 1.0 milliamp to1.5 V or 1.5 milliamps, etc. up to 8.0 V or 8.0 milliamps with noadverse side effects observed. However, increasing the intensity another0.5 V or milliamp interval, from 8.0 V or 8.0 milliamps to 8.5 V or 8.5milliamps may result in a decreased beta band signal but may also resultin an adverse side effect. As a result, the intensity that maximallysuppresses the beta band signal may be determined to be 8.0 V or 8.0milliamps, which is the intensity that suppresses the beta band signalthe most without also causing adverse side effects. Adverse side effectsmay include, for example, eye twitching, facial muscle twitches, speechdifficulties, visual side effects, or other problematic side effects.Such side effects may be monitored with diagnostic tools and/ormanually, such as visually, by a clinician.

After the responsiveness of the beta band signal to electricalstimulation is determined for the position corresponding to 108 a for aplurality of intensities of electrical stimulation, electricalstimulation may be delivered at other positions to determine theresponsiveness of the beta band signal to electrical stimulation atthose positions. In some examples, the first electrical stimulation tobe delivered at the other positions may be determined based on theintensity determined to be suppressive at the position corresponding to108 a. For example, for the position corresponding to 108 b, where thenormalized local field potential was determined to be “0.9” whennormalized with respect to the local field potential at the positioncorresponding to 108 a, the first intensity of electrical stimulation tobe delivered may be 0.9 times the intensity determined to maximallysuppress the beta band signal at the position corresponding to 108 a (10V or 10 milliamps). For example, the first intensity to be delivered atthe position corresponding to 108 b may be 0.9×10 V or 10 milliamps,which is 9 V or 9 milliamps.

Sensing circuitry 206 may sense the beta band signal at the positioncorresponding to 118 b when electrical stimulation is not delivered. Thebeta band signal may be, for example 9 μV. Controller 202 and/orcontroller 302 may control electrical stimulation circuitry 204 todeliver electrical stimulation at 9V or 9 milliamps and sensingcircuitry 206 may sense the beta band signal resulting from thedelivered electrical stimulation. The resulting beta band signal may be,for example, 1.5 μV, such that the delivery of the electricalstimulation reduced the sensed beta band signal from 9 μV to 1.5 μV.Electrical stimulation intensity may be increased, for example, inintervals of 0.5 V or 0.5 milliamp to determine whether increases in theintensity results in additional suppression. In some cases, additionalsuppression may not result from increases in intensity from the firstintensity used. For example, increases to 9.5 V or 9.5 milliamps and10.0 V or 10.0 milliamps may still result in the same sensed beta bandsignal of 1.5 μV. In some examples, intensity may be decreased todetermine whether the first delivered electrical stimulation was of thesmallest intensity that maximally suppresses the beta band signal. Forexample, the intensity may be decreased from 9.0 V or milliamps to 8.5 Vor milliamps to determine whether the beta band signal sensed inresponse increases. If it does increase as the intensity is decreased,then the originally delivered intensity may be the intensity thatmaximally suppresses the beta band signal. If decreasing the intensityresults in an increase in the beta band signal, then the originallydelivered stimulation may be determined to be the intensity thatmaximally suppresses the beta band signal. If decreasing the intensityof electrical stimulation delivered does not result in an increase inthe beta band signal, then the intensity may be decreased in intervalsuntil the lowest intensity that does not result in an increase in thebeta band signal is determined and that intensity may be determined tothe be intensity that maximally suppresses the beta band signal.

For the position corresponding to 118 b, as with the positioncorresponding to 118 a, patient 106 may be monitored for desirableeffects and/or for adverse side effects to help determine the intensitythat maximally suppresses the beta band signal but does not result inadverse side effects and to determine responsiveness to electricalstimulation, including changes in response to changes in intensity ofthe electrical stimulation.

In some examples, delivered electrical stimulation at some positions maynot result in a decrease in the beta band signal. For example, for eachof the positions corresponding to 118 c and 118 d, electricalstimulation may be delivered at a plurality of intensities and the betaband signal may be sensed in response to the delivered electricalstimulation. However, the delivery of electrical stimulation at each ofthe plurality of intensities may be determined to not decrease the betaband signal from the beta band signal sensed when no electricalstimulation is delivered. Thus the intensity of electrical stimulationthat maximally suppresses the beta band signal at those positions may bedetermined to be zero and the beta band signal may be determined to haveno response to electrical stimulation.

Based on the responsiveness of the beta band signal to electricalstimulation at each of the positions corresponding to electrodes 108 a,108 b, 108 c, and 108 d, controller 202 and/or controller 302 may definea therapy target. The therapy target definition may include informationthat may be used to select parameters for delivering therapy, forming alesion, monitoring the size and position of source 108, monitoring theposition of lead 114 with respect to source 108, and/or for any othersuitable purpose according to particular needs. The information includedin the therapy target definition may include, for example, the intensityof electrical stimulation that maximally suppresses the beta band signalfor each of the positions. These may be, for the example describedabove, 10 V or milliamps for the position corresponding to 108 a, 9 V ormilliamps for the position corresponding to 108 b, 0 V for the positioncorresponding to 108 c, and 0 V for the position corresponding to 108 d.The information may also include, for example, the sensed local fieldpotentials at each of the positions when electrical stimulation is notdelivered. The values may include, for example, the values with respectto reference value or normalized values as described above with respectto the example shown in FIG. 5. For example, the normalized values forthe positions corresponding to each of 118 a, 118 b, 118 c, and 118 d,may be 1.0, 0.9, 0.7, and 0.5, respectively. Any other suitableinformation may also be included in the definition of the therapytarget. The responsiveness of the beta band signal to electricalstimulation at each of a plurality of positions may also be included inthe definition of the therapy target.

In some examples, the defined target may define a spatial extent ofsource 118. For example, based on the responsiveness of the beta bandsignals to electrical stimulation at each of the positions in theexample above, controller 202 and/or controller 302 may determine thatsource 108 is adjacent to the positions corresponding to electrodes 118a and 118 b (i.e., span the length of those positions) becauseelectrical stimulation delivered at those positions suppresses the betaband signal sensed at those positions.

For each of the positions corresponding to 118 a and 118 b that aredetermined to be adjacent to source, controller 202 and/or controller302 may also determine the span of source 108 in the radial directionaway from the position. A width of source 108 adjacent to any particularposition along lead 114 may be, for example, in the range of 0.01-50 mm,or in the range of between 0.1-10 mm, and the information obtained bythe iterative process of sensing the local field potentials and betaband signals at the plurality of positions and determining theresponsiveness of the beta band signals or some other biomarker of thesensed signal that indicates responsiveness to electrical stimulationfor each position, may be used to determine the span and position of thesource 108 with respect to the lead 114.

For example, beta band signals may be sensed along the lead 114. Insequence, as described above, or simultaneously, stimulation pulses maybe delivered and titrated (with different amplitude pulses) to determinethe responsiveness or sensitivity to stimulation along the length oflead 114. A large beta signal at one position along the lead may suggestthat a dysfunctional tissue is near the position. The tissue may,however, be a nearby tissue that is moderately dysfunctional or a moredistant tissue that is more significantly dysfunctional. Both of theseconditions may result in the observed beta signal. But beta suppressivestimulation of different magnitudes can be delivered along thetrajectory and may allow differentiation of an appropriate distanceestimate for the dysfunctional tissue relative to the trajectory. Asmall stimulation may produce a small field. Suppression of the betasignal by a small stimulation may indicate a dysfunction source nearerto the trajectory. Alternatively, if the small signal does not suppressthe beta signal, the dysfunction source may be estimated to be furtherfrom the trajectory.

By determining the responsiveness of the beta band signals to electricalstimulation, controller 202 and/or controller 302 may determine anextent of source 108 in a direction away from lead 114 for each of theselected positions, including positions corresponding to electrodes 118a and 118 b. For example, the intensity needed to suppress a signal at agiven position may indicate a larger extent of source 108 away from lead114. For example, the larger the intensity needed to suppress the signalsensed at a particular position, the further that source 108 may extendaway from lead 114. For example, a larger intensity may be needed at aposition corresponding to electrode 118 a than at the positioncorresponding to electrode 118 b because source 108 extends further fromlead 114 at the position corresponding to electrode 118 a.

In combination with one or more electrical signals sensed whenelectrical stimulation is not delivered the responsiveness of the betaband signals to electrical stimulation may be used to define a spatialextent of source 108. For example, the responsiveness of the beta bandsignals to electrical stimulation may help to differentiate between aclose and small source and a large and far away source that may eachresult in a similar sensed signal when electrical stimulation is notdelivered. Using this information, controller 202 and/or controller 302may define a therapy target that includes, for example, a spatialmapping of source 108.

In some examples, controller 202 and/or controller 302 may record afirst intensity at which suppression of the beta band signal firstoccurs and a second intensity at which maximal suppression is achieved(additional increases in intensity does not further suppress the betaband signal or the beta band signal is suppressed by a predeterminedthreshold amount or to be under a predetermined threshold amount). Thefirst intensity may be indicative of a near edge of the source and thesecond intensity may be indicative of the far edge of the source.

This iterative process of stimulation and sensing may be performed foreach position within brain 106 determined to be of interest. Forexample, in the example of FIGS. 4A and 6A, this process may beperformed for the positions corresponding to each of electrode 118 a,118 b, 118 c, and 118 c. Suppressive stimulation field 602 a isrepresentative of a stimulation field at the position corresponding toelectrode 118 a that is a function of an intensity of the stimulationthat maximally suppresses beta band signals sensed at the position bymaximally reducing the power or amplitude of the beta band signal. Insome examples, other indications of suppression or enhancement such as,for example, patient responses, including movements, that indicatesuppression of an undesired signal or enhancement of a desired signal,may be used to indicate that the responsiveness of the beta band signalto electrical stimulation. Suppressive stimulation field 602 b isrepresentative of stimulation field at the position corresponding toelectrode 118 a that is a function of an intensity of stimulation thatsubstantially suppresses beta band signals sensed at the position.Examples of intensities of electrical stimulation that may be sufficientto suppress beta band signals may be, for example, in the range ofapproximately 1.5 volts to 5 volts or 1.5 milliamps to 5 milliamps. Forsome applications, higher voltages or current may be needed to maximallysuppress the desired signal, for example 5 to 10 volts or 5 to 20milliamps. As described above, in the illustrated example, no intensityof electrical stimulation may result in suppression of the beta bandsignal at the positions corresponding to 118 c and 118 d such that nosuppressive stimulation field is shown for those positions.

Based on the responsiveness of the beta band signals to electricalstimulation and the electrical signals sensed when electricalstimulation was not delivered, controller 202 and/or controller 302 maydefine a therapy target corresponding to a spatial extent of source 108.For example, as described above, the responsiveness of the beta bandsignals to electrical stimulation at a particular position may indicatethe extent of the source 108 in a radial direction away from theposition, with a larger intensity needed to suppress the signalindicating a further extent of the source 108 away from the lead 114,and the electrical signal sensed when electrical stimulation is notdelivered may further indicate the span of source, with a source 108 ofa particular size having a larger sensed signal when closer to theposition on lead 114. In some examples, controller 202 and/or controller302 may control delivery of therapy to brain 106 of patient 104 based onthe therapy target definition. For example, based on the therapy targetdefinition corresponding to a spatial definition of source 108,controller 202 and/or controller 302 may control delivery of therapyincluding electrical stimulation to treat source 108, electricalstimulation to create a lesion corresponding to the spatial extent ofsource 108, and/or any other suitable therapy. Controller 202 and/orcontroller 302 may control parameters such as stimulation amplitude,frequency, and/or pulse width in order to adjust intensity to tailortherapy to source 108 based on the therapy target definition.

In some examples, the stimulation intensity at each position thatmaximally suppresses beta activity can be used directly for a finalclinical setting in which therapy is delivered by deliveringcorresponding electrical stimulation at the intensity for eachcorresponding position. In other examples, a spatial mapping of thesource may be stored based on the maximally suppressive intensities andthe mapping may be used to select therapy parameters.

The combination of the sensed local field potential amplitude whenelectrical stimulation is not delivered and the response of a sensedsignal to electrical stimulation at one or more positions may be used tospatially map the source 108. For example, measurements for local fieldpotential amplitudes may be in the range of approximately 0.02 to 10 μV.As an example, a point source for highly dysfunctional tissues that area small distance from the measurement electrode may produce a highamplitude signal without stimulation. As electrical stimulationamplitude is increased (for example from 0 to 10 V) the electrical fieldmay extend away from the stimulation lead from approximately 0 mm to −8mm. The relationship between the stimulation amplitude and the localfield potential measurement may reveal the size or volume of thedysfunctional tissue. For example a steady constant but small (forexample slope=−(0.05−0.15)μV/V) decrease with stimulation amplitudeincrease may suggest that dysfunction is spread throughout or moreevenly across the tissue. Conversely a rapid and large decrease withstimulation amplitude (for example slope=−0.2−3 μV/V) beginning at aspecific amplitude may reveal a proximal margin of the dysfunctionaltissue has been identified by the stimulation. In this manner,combinations of stimulation and sensing can be used to identify basictissue dysfunction states, approximate locations and volume within thebrain tissue near the site. Additionally and in a similar manner,changes in patient responses, such as changes in disorder symptomsdescribed above, as a result of changes in stimulation intensity, may beused in addition or alternatively to define the spatial extent of thetherapy target.

Although the illustrated examples describe delivering electricalstimulation to suppress a sensed signal characteristic, electricalstimulation may be delivered, in some example applications, to furtherenhance, rather than suppress, a sensed signal characteristic. Forexample, controller 202 and/or controller 302 may control electricalstimulation circuitry 204 to deliver electrical stimulation and sensingcircuitry 206 may sense electrical signals resulting from the deliveredstimulation to identify the intensities of electrical stimulation thatenhance the sensed signal characteristic. A therapy target may bedefined based on the responsiveness of the sensed signal characteristicto electrical stimulation for each of a plurality of positions and thetherapy target definition may be used to select therapy parameters andto deliver therapy, form a lesion, monitor source 108 and/or theposition of lead 114 and electrodes 118 with respect to source 108,and/or for any other suitable purpose.

During delivery of electrical stimulation for definition of the target,each selected electrode, electrode segment, and/or group of electrodes,such as 118 a, 118 b, 118 c, and 118 d in this example, may deliverelectrical stimulation individually in a unipolar manner with anotherelectrode in IMD housing 112, or in a bipolar manner with anotherelectrode on lead 114. During delivery of therapy, delivery of therapymay be via all of the selected electrodes, such as electrodes 118 a, 118c, 118 c, and 118 d, whether simultaneously or at least in a temporallyoverlapping manner, or by delivery via different electrodescorresponding to particular time slots. Therapy can be delivered usingunipolar or bipolar stimulation.

FIG. 6B illustrates an example including lead 114 with electrodes 118adjacent to spherical source 408. As described with reference to FIGS.4B and 5, local field potentials may be sensed at each of the positionscorresponding to electrodes 118 a, 118 b, 118 c, and 118 d. Based on thesensed local field potentials, as shown in FIG. 5, controller 202 and/orcontroller 302 may determine that the position corresponding toelectrode 118 a has the largest sensed local field potential whenelectrical stimulation is not delivered. Thus, controller 202 and/orcontroller 302 may control electrical stimulation circuitry 204 to firstdeliver electrical stimulation at a position corresponding to electrode118 a. For example, controller 202 and/or controller 302 may controlelectrical stimulation circuitry 204 to deliver electrical stimulationat the position via electrode 118 a. In other suitable examples,electrical stimulation may be delivered to positions corresponding toeach of 118 a, 118 b, 118 c, and 118 d in any suitable order and/orsimultaneously. In some examples, electrical stimulation may only bedelivered at selected positions based on the local field potentialsensed at each of the positions when electrical stimulation is notdelivered.

As described with reference to FIG. 6A, an iterative process ofdelivering electrical stimulation at a plurality of intensities, forexample, at a plurality of increasing intensities, and sensingelectrical signals in response to the delivered electrical stimulation,may be performed to determine the responsiveness of the beta bandsignals to electrical stimulation. The intensity of suppressivestimulation may be represented by suppressive stimulation field 604,corresponding to an electrical stimulation that substantially suppressesbeta band signals sensed at the position corresponding to electrode 118a or otherwise suppressing beta band signals to satisfy a predeterminedcriteria. The responsiveness of the beta band signals to electricalstimulation as determined by this process, may be used by controller 202to define a therapy target corresponding to source 408. In someexamples, defining the therapy target may be further based on the localfield potentials sensed before delivery of electrical stimulation asdescribed with reference to FIGS. 4B and 5. In some examples, thetherapy target definition may correspond to a spatial definition ofsource 408. In some examples, the therapy target definition may beinformation indicating the responsiveness of the beta band signals toelectrical stimulation at one or more positions, a responsiveness ofsome other biomarker to electrical stimulation, local field potentialssensed when electrical stimulation is not delivered, and/or parametersor other information that are a function of the responsiveness of thebeta band or other biomarker signals to electrical stimulation at one ormore positions and/or local field potentials. Examples of otherbiomarker signals may include time-domain characteristics of a sensedsignal, such as an instantaneous or time-averaged signal amplitudeexceeding or dropping below a high or low threshold, respectively. Otherexamples may include a particular waveform morphology as may bedetermined based on template matching, or any other sensedcharacteristic in the time or frequency domain that is indicative ofresponsiveness (e.g., responsiveness of affected tissue) to stimulation.In some example, the defined target may be used for determiningparameters for therapy delivery, whether or not the therapy targetdefinition is indicative of a spatial extent of source 108.

In some examples, the iterative process of delivering electricalstimulation and sensing electrical signals to determine theresponsiveness of the beta band signals to electrical stimulation mayalso be performed for other positions along lead and may, in someexamples, not result in suppression of the beta band signal such that noresponsiveness of the beta band signals to electrical stimulation isdetermined.

FIG. 6C illustrates an example including lead 114 with electrodes 118adjacent to source 608. A similar process, as described with referenceto FIGS. 6A-6B may be performed to sense local field potentials at eachof positions corresponding to electrodes 118 a, 118 b, 118 c, and 118 dof lead 114 (in some examples, select positions based on the sensedlocal field potentials), and iteratively deliver stimulation and sensebeta band signals at the plurality of (selected) positions to determinea therapy target definition. Suppressive stimulation fields 606 a and606 b may correspond to stimulations at intensities sufficient tosuppress beta band signals sensed at each of the selected positions.Suppressive stimulation fields 606 a and 606 b may be substantiallysimilar to suppressive stimulation fields 602 a and 602 b, respectively,of FIG. 6A for triangular source 108. However, the responsiveness of thebeta band signals to electrical stimulation for each case may be used,in combination with sensed local field potentials for each of theselected positions, to determine information representative of a therapytarget that corresponds to the spatial extent of each of source 108 andsource 608. The representative information may, for example, indicatepositions at which a sensed local field potential is over a thresholdamount, a function of the sensed local field potentials at one or morepositions, intensities or functions of intensities for suppressivestimulation at one or positions, and/or other information indicating theresponsiveness of the beta band signals to electrical stimulation at oneor more positions.

For example, although suppressive stimulation field 606 a may be similarto suppressive stimulation field 602 a, each corresponding to a positioncorresponding to electrode 118 a, such that the intensity of thesuppressive stimulation at each of those positions are similar, a localfield potential sensed at the position may be lower in the example ofsource 608 than in the example of source 108 due to the greater distancebetween the portion of source 608 adjacent to lead 114 and lead 114 thanthe distance between the portion of source 108 adjacent to lead 114 andlead 114. However, both the sensed local field potentials at each of thepositions corresponding to electrodes 118 a and 118 b and thedetermination of the intensity of electrical stimulation sufficient tosuppress beta band signals at those positions may be used together bycontroller 202 to define a therapy target that corresponds to a spatialextent of a source and to thus differentiate between these differentsource shapes and locations. Additionally, the responsiveness of thebeta band signals to electrical stimulation at the positioncorresponding to electrode 118 a may be used to determine the positionof the source adjacent to the position, as described in further detailabove with reference to FIG. 6A.

More generally, a source that is close to a position on lead 114 mayresult in a sensed local field potential that is larger than if thesource were further away. A source that extends far away from theposition on lead 114 may require a larger intensity for suppression thanif the source did not extend as far. Thus, for a given position, a smallsensed local field potential and a large intensity of stimulation neededfor suppression may indicate that the source is far from the position onlead 114 and extends out in the radial direction from lead 114 by asmall amount, i.e., the portion corresponding to that position is closeand small. A large sensed local field potential and a large intensity ofstimulation needed for suppression may indicate that the source is closeto the position of lead 114 and extends out in the radial direction fromlead 114 by a large amount, i.e., the portion corresponding to thatposition is close and large. Additionally or alternatively, theresponsiveness of the beta band signals to electrical stimulation at oneor more positions may be used to determine the boundaries of source 108within brain 106. Using these determinations for multiple positionsalong and/or about the longitudinal axis of lead 114, i.e., at differentlongitudinal positions along the length of the lead and/or at differentangular positions around the circumference of the lead, may allow forconstructing a 3-dimensional mapping of the shape of the source 108within brain 106.

FIGS. 7A and 7B are diagrams illustrating cross-sectional views ofexample electrode configurations for delivering electrical stimulationat a plurality of different intensities at each of a plurality ofdifferent positions within brain 106 of patient 104 and sensingelectrical signals at each of the different positions in response to theelectrical stimulation taken along lines 7A-7A and 7B-7B of FIG. 6A,respectively.

FIG. 7A includes a cross-sectional view of lead 114, electrode 118 a,and source 108 taken along the line 7A-7A in FIG. 6A. As described abovewith reference to FIGS. 1A and 1B, one or more of electrodes 118 mayinclude segmented electrodes or other types of electrodes that may allowfor delivery of stimulation and/or sensing in any suitablecircumferential position about lead 114. For example, electrode 118 amay include a plurality of segments 718 a-718 f extending arounddifferent circumferential portions of the lead, and each correspondingto a different circumferential position A-F. As another example,electrode 118 a may include a segmented electrode that extends aroundless than the entire circumference of the lead and that allows forstimulation and/or sensing in one particular circumferential directionabout lead 114 at a time (has partial ring contact) and may be rotated,for example by motor 122 of FIG. 1A during implantation, to deliverstimulation and/or sense at each of the circumferential positions A-F.

As described with reference to FIGS. 5A-5C, local field potentials maybe sensed at a plurality of positions within brain 106 and, in theillustrated example of FIG. 7A, they may be sensed at each of thecircumferential positions A-F, by segments 718 a-718 f of electrode 118a corresponding to different circumferential positions A-F and/or byrotation of electrode 118 a.

In some examples, selected positions may be determined to be of interest(for further analysis including delivery of electrical stimulation andsensing of electrical signals in response to the delivered electricalstimulation) based on the sensed local field potentials. In otherexamples, positions may be of interest based on determining thatelectrical stimulation suppresses an electrical signal at that position.For example, circumferential positions A, B, and F may be of interestwhile circumferential positions C-E may not be of interest based on thelocal field potentials sensed or the suppression of electrical signalsby electrical stimulation for each position A-F. In some examples,controller 202 and/or controller 302 may be configured to control therotation of lead 114 and/or the sensing of segments 718 a-718 f ofelectrode 118 a about lead 114 to determine circumferential selectedpositions by sensing and/or delivering stimulation at predeterminedintervals about lead 114, in either direction about lead 114 until aparticular position is not of interest (because the sensed local fieldpotential sensed at that position is under a threshold amount or becausea sensed signal at that position is not suppressed by delivery ofelectrical stimulation). For example, controller 202 and/or controller302 may be configured to control sensing of local field potential and/ordelivery of electrical stimulation at circumferential position A, thenF, then E. When the local field potential is under a threshold amount ora sensed signal is not suppressed in response to electrical stimulationat position E, such that position E is determined not to be of interest,controller 202 and/or controller 302 may control sensing and/ordelivering electrical stimulation at circumferential position B, then C,until, again a position, in this example position C, is determined tonot be of interest. In this way, controller 202 and/or controller 302may limit unnecessary sensing and/or delivery of electrical stimulationat circumferential positions about lead 114, such as, in this example,circumferential position C.

The iterative process of delivering stimulation at different intensitiesand sensing beta band signals until the beta band signals aresufficiently suppressed may be performed for each of positions A, B, andF. This process may also be performed, for example, at position E or anyother suitable position. Controller 202 and/or controller 302 may thenfurther define a therapy target corresponding to source 108 based on thesensed local field potentials and the responsiveness of the beta bandsignals to electrical stimulation for each of the circumferentialpositions. For example, the local field potential and the responsivenessof the beta band signals to electrical stimulation for circumferentialposition A may help to define a therapy target indicative of the spatialextent of source 108 in the direction of circumferential position A,which may be different than that determined for circumferentialpositions B and F. For example, for delivery of electrical stimulationtherapy, a given electrode may have an intensity that is selected as afunction of the intensity that achieved suppression of the beta bandsignal by a desired degree. Additionally, the local field potentialssensed and the responsiveness of the beta band signals to electricalstimulation for each of the circumferential positions A, B, and F mayhelp to further define a therapy target that may, in some cases,represent a spatial extent of source 108. Positions such as position Cmay be determined to not be adjacent to the source because delivery ofelectrical stimulation at that position does not result in suppressionof a sensed electrical signal at that position.

Although electrode segments 718 a-718 f and 718 g-7181 are described ascorresponding to axial positions corresponding to electrodes 118 a and118 b, any suitable number of electrode segments may be included on lead114 at any suitable axial and/or circumferential positions. For example,additional electrode segments may be included at axial positionscorresponding to electrodes 118 c and 118 d.

For selected axial positions, based on sensed local field potentials atone or more axial positions, this process of sensing local fieldpotentials and/or determining the responsiveness of the beta bandsignals to electrical stimulation for any number of suitablecircumferential positions may be performed, for example, using differentsegmented electrodes and/or by rotation of lead 114.

FIG. 7B includes a cross-sectional view of lead 114, electrode 118 bwith electrode segments 718 g-7181, and source 108 taken along the line7B-7B in FIG. 6A. As described with reference to FIG. 7A, local fieldpotentials may be sensed and/or electrical stimulation may be deliveredat each of circumferential positions G-L. In some examples, position Lmay be determined to be of interest because delivery of electricalstimulation results in suppression of a sensed signal at that position.Using the sensed local field potentials and the responsiveness of thebeta band signals to electrical stimulation for each of the selectedcircumferential positions for selected positions along leadcorresponding to electrodes 118 a and 118 b, a therapy target may bedefined by controller 202 that corresponds to a 3-dimensional spatialextent of source 108. In some examples, the therapy target definitionmay not necessarily correspond to a 3-dimensional spatial extent ofsource 108 but may be used to derive therapy parameters for therapy ofsource 108. For example, one of more treatment parameters may be afunction of the responsiveness of the beta band signals to electricalstimulation and/or the sensed local field potentials for the axialand/or circumferential positions.

As described in the previous examples, signals sensed when electricalstimulation is not delivered, as well as the responsiveness of the betaband signal to changes in electrical stimulation may be used todetermine a mapping of the source. This process of sensing and thendelivering while sensing may be performed at multiple axial positionsalong the lead for one circumferential position to create a2-dimensional mapping of the source in the plane of the circumferentialdirection. Using segmented electrodes to perform this process formultiple circumferential directions may allow for producing multiple2-dimensional mappings, one for each circumferential position, which maybe combined to perform a 3-dimensional mapping of the source.

In some examples, the 2-dimensional or 3-dimensional mappings may bedefined by the local field potentials sensed when electrical stimulationis not delivered and/or one or more intensity levels of electricalstimulation delivered and the response of the beta band signals to thestimulation signals at the corresponding intensities at each electrodeto spatially define the source. In other examples, measurements of localfield potentials sensed when electrical stimulation is not deliveredand/or one or more intensity levels of electrical stimulation deliveredand the response of the beta band signals to the stimulation signals atthe corresponding intensities at each electrode may be converted tospatial coordinates, shapes, sizes, etc. that may be stored and used toselect parameters, monitor changes, etc. In this manner, defining thetherapy target (as a 2D or 3D mapping or otherwise) may comprisedefining parameters for delivering therapy, including, for example,selecting electrodes for delivery of electrical stimulation and/orselecting intensities of electrical stimulation delivered by theselected electrodes. For example, selected electrodes and selectedintensities may define the therapy target and directly form parametersfor delivery of electrical stimulation. In other examples, the therapytarget may be defined and then the stimulation parameters may beselected based on the therapy target definition such that the parametersfor delivering stimulation therapy are different from the parametersthat define the therapy target.

FIGS. 8A and 8B are diagrams illustrating another example electrodeconfiguration for delivering electrical stimulation at a plurality ofdifferent intensities at each of a plurality of different positionswithin brain 106 of patient 104 and sensing electrical signals at eachof the different positions in response to the electrical stimulation.

Lead 814 may be an example lead similar to lead 114 of FIGS. 1A-6B.Electrode 818 may be an example electrode similar to each of electrodes118 of FIGS. 1A-7B and/or may include a group of electrodescorresponding to one or more axial positions along the length of lead814. Lead 814 and electrode 818 may be controlled by controller 202 toperform the process described with reference to FIGS. 4A-8B. Instead ofusing different electrodes along a lead to sense local field potentialsand perform the iterative process to determine the responsiveness of thebeta band signals to electrical stimulation, the same electrode or groupof electrodes 818 may be used while lead 814 is positioned within brain106. For example, motor 122 may be a step-wise motor for advancing lead814 within brain 106. As lead 818 advances within brain 106, electrode818 may sense local field potentials, including at several positionsaxial along the longitudinal axis of lead 818. Lead 818 may also senselocal field potentials at several circumferential positions usingsegments of a segmented electrode and/or rotation of lead 118 aboutlongitudinal axis of lead 818.

The iterative process as described with reference to FIGS. 6A-7B may beperformed to determine the responsiveness of the beta band signals toelectrical stimulation for each of the selected positions. In someexamples, the iterative process may be performed only for positions atwhich the sensed local field potentials are over a threshold amount. Inother examples, the iterative process may be performed at all positions.In other examples, the iterative process may be performed for eachposition until a boundary of the source is determined at whichelectrical stimulation does not result in suppression of a sensed signalwhen the electrical stimulation is delivered, at which point positionsbeyond the boundary may not be used for delivery of electricalstimulation and sensing of a change in a signal in response to thestimulation, as described above. Based on the sensed local fieldpotentials and the responsiveness of the beta band signals to electricalstimulation for one or more positions, controller 202 and/or controller302 may define a therapy target corresponding to a spatial extent ofsource 108. The process of sensing local field potentials anddetermining the responsiveness of the beta band signals to electricalstimulation may be performed in any suitable order. For example, lead814 may be placed as shown in FIG. 8A and local field potentials may besensed at one circumferential position about lead 814 and theresponsiveness of the beta band signals to electrical stimulation may bedetermined at that position before rotation and performing these stepsfor another circumferential position or advancing lead 814. As anotherexample, local field potentials may be sensed for each of multiplecircumferential positions about lead 814, lead 814 may be advanced(lowering lead 814 to the target brain tissue), and local fieldpotentials may be sensed at circumferential positions about lead 814until all selected positions, whether circumferential or along lead 814,are determined, and then the responsiveness of the beta band signals toelectrical stimulation may be determined for each of the selectedpositions. Any other suitable order of steps may be formed according toparticular needs. In some examples, suppressive electrical stimulationmay be determined in a sequence as a function of the sensed local fieldpotentials. For example, suppressive electrical stimulation may bedetermined first at the position with the highest sensed local fieldpotential, then at the position with the second highest local fieldpotential, and so on.

Lead 814, lead 114, or any suitable lead may be used to define a therapytarget and/or to deliver therapy. A lead may be a chronic lead used todefine the therapy target and for chronic treatment within brain 106 ormay be a test lead for defining the therapy target and may be removedbefore therapy is delivered based on the defined target using anotherdevice. Additionally, a lead may be used to define a therapy target,deliver short-term therapy based on the therapy target definition, andsubsequently removed from brain 106.

FIG. 9 is a flow diagram of an example technique for defining a therapytarget, selecting therapy parameters based on the therapy targetdefinition, and delivering therapy to brain 106 of patient 104 based onthe selected parameters.

Electrical stimulation may be delivered at a plurality of differentintensities at each of a plurality of different positions within brain106 of patient 104 via selected combinations of electrodes 108 (902).For example, controller 202 and/or controller 302 may control electricalstimulation circuitry 204 to deliver electrical stimulation at aplurality of different intensities at each of a plurality of differentpositions within brain 106 of patient 104 via selected combinations ofelectrodes 108. For example, as described with respect to FIGS. 4A-8B,controller 202 and/or controller 302 may control electrical stimulationcircuitry 204 to deliver electrical stimulation at a plurality ofselected positions including, for example, a plurality of axialpositions along a length of lead 114 and/or a plurality ofcircumferential positions about a circumference of lead 114. Electricalstimulation may be delivered at a plurality of intensities including,for example, at progressively larger intensities to identify theresponsiveness of the beta band signals to electrical stimulation ateach position.

Electrical signals may be sensed at each of the plurality of differentpositions within the brain 106 of the patient 104 in response to theelectrical stimulation delivered at each of the plurality of differentpositions at the plurality of different intensities (904). For example,sensing circuitry 206 may sense electrical signals at each of thedifferent positions within brain 106 of patient 104 in response to theelectrical stimulation delivered at each of the different intensities.For example, as described with reference to FIGS. 4A-8B, sensingcircuitry 206 may sense beta band signals at each of the axial and/orcircumferential positions to determine the responsiveness of the betaband signals to electrical stimulation for each position. For example,sensing circuitry 206 may sense beta band signals as each of theprogressively larger stimulation intensities are delivered to sense betaband signals corresponding to each of the intensities of electricalstimulation delivered for each of the positions. In some examples,sensing circuitry 206 may sense beta band signals as each of theprogressively larger stimulation intensities are delivered andcontroller 202 and/or controller 302 may identify the first intensity ofelectrical stimulation to substantially suppress beta band signals by apredetermined amount by, for example, limiting beta band signals morethan other intensities. In some examples, at some positions, delivery ofelectrical stimulation may not result in suppression of electricalstimulation such that no suppressive intensity is determined for thatposition. Controller 202 and/or controller 302 may further determine theresponsiveness of the beta band signals to electrical stimulation at oneor more positions.

In some examples, sensing the electrical signals comprises sensing theelectrical signals at each of the different positions via a plurality ofelectrodes, such as electrodes 118 a and 118 b, implanted proximate torespective positions of the plurality of different positions, andwherein the plurality of different positions comprise combinations of aplurality of axial positions along a length of lead 114 and a pluralityof circumferential positions about a circumference of lead 114.

A therapy target may be defined based on the sensed electrical signalsto provide a therapy target definition (906). For example, controller202 and/or controller 302 may define a therapy target definition basedon the sensed electrical signals. For example, based on the deliveredelectrical stimulation and the sensed beta band signals in response tothe delivered electrical stimulation, controller 202 and/or controller302 may define a therapy target corresponding to the source of betaoscillation, such as, for example, source 108, that may correspond to aspatial extent of source 108. Controller 202 and/or controller 302 maydo so, for example, at least in part by determining the responsivenessof the beta band signals to electrical stimulation. For example, asprogressively larger stimulation intensities are delivered for aparticular position and beta band signals are sensed in response to eachprogressively larger stimulation intensity, controller 202 and/orcontroller 302 may identify the responsiveness of the beta band signalsto electrical stimulation. Controller 202 and/or controller 302 mayfurther compare sensed beta band signals for each intensity to those ofother intensities and determine the intensity that suppresses the betaband signal the most or just as well as other intensities. The therapytarget definition may be further defined based on local field potentialssensed at each position when electrical stimulation is not delivered.

In some examples, defining the therapy target definition may comprisedefining parameters, including, for example, selecting electrodes and/orintensities for delivering electrical stimulation for therapy. In suchexamples, the defined parameters may be representative of a therapytarget definition that is a function of a spatial extent of the source.For example, selected electrodes and selected intensities may define thetherapy target and directly form parameters for delivery of electricalstimulation. In other examples, the therapy target may be defined andthen the stimulation parameters may be selected based on the therapytarget definition.

In some examples, the therapy target definition may not indicate aspatial extent of source 108, although it may include information thatmay be used to indicate a spatial extent of source 108. For example, thetherapy target definition may include information, such as theresponsiveness of the beta band signals to electrical stimulation at oneor more positions, which may be used by controller 202, programmer 120,or any other suitable device to create a spatial mapping of source 108.In other examples, the therapy target definition may indicate thespatial mapping of source 108.

In some examples, controller 202 and/or controller 302 may convert thetherapy target definition to a graphical representation of the spatialextent of source 108 for display to a user. The graphical representationmay be displayed, for example, via user interface 304 for use by a userduring programming of IMD 110 and/or at any other suitable time,including during implantation, testing, and/or after implantation oflead 114, according to particular needs. The graphical representationmay be used by a user to help select therapy programs and/or therapyparameters and/or to monitor source 108, including changes to source108, and/or a position of lead 114 and/or electrodes with respect tosource 108.

One or more parameters of therapy to be delivered to a brain of apatient may be selected based on the therapy target definition (908).For example, controller 202 and/or controller 302 may select one or moreparameters of therapy to be delivered to brain 106 of patient 104 basedon the therapy target definition. For example, controller 202and/programmer 120 may select therapeutic electrical stimulationparameters based the therapy target definition. For example, controller202 and/or controller 302 may select intensities for deliveringelectrical stimulation that are equal to or otherwise derived from theintensities determined to suppress beta band signals and/or otherwisebased on the responsiveness of the beta band signals to electricalstimulation at one or more positions, as determined to define thetherapy target. As another example, controller 202 and/or controller 302may select positions and/or specific electrodes, electrode segments,and/or groups of electrodes for delivering therapeutic electricalstimulation.

The therapy target definition may include information indicatingselected positions and the responsiveness of the beta band signals toelectrical stimulation at each of those positions. This information mayallow for selecting parameters that may include intensities that may bedelivered for each of the positions that may substantially suppress betaband signals at those positions and may, for example, suppress otherunwanted symptoms related to a corresponding source, such as source 108,of beta oscillations. In some examples, a selected parameter may includean intensity for a given position that may be different than anintensity identified by the therapy target definition to substantiallysuppress beta band signals. For example, intensities determined tosubstantially suppress beta band signals, as indicated in the therapytarget definition, may be used to formulate a therapy program that mayinclude applying intensities that are different than the suppressiveintensities but are based on the suppressive intensities. For example,the therapy program may include delivering electrical stimulation atintensities that are a function of the determined intensities ofsuppressive stimulation and/or otherwise based on the responsiveness ofthe beta band signals to electrical stimulation at one or morepositions.

As one example, a therapy target definition may indicate a firstsuppressive intensity of electrical stimulation corresponding to a firstposition, a second suppressive intensity of electrical stimulationcorresponding to a second position, and a third suppressive intensity ofelectrical stimulation corresponding to a third position. Selectingtherapy parameters may include selecting one or more amplitudes,frequencies, and/or pulse widths as functions of the first intensity,the second intensity, and/or the third intensity. The selected therapyparameters may be chosen to target the source 108 based on the exampletherapy target definition. In such an example, defining the therapytarget may or may not include constructing a mapping of the source 108but the parameters may still be selected to target the spatial extent ofsource 108 based on the responsiveness of the beta band signals toelectrical stimulation at the corresponding positions in the therapytarget definition.

In other examples, a mapping of the spatial extent of source 108, asdetermined when defining the therapy target, may be used to selecttherapy parameters to target the source 108 based on the mapping. Insome examples, the selected parameters may be based on the mappingand/or other information, such as suppressive intensities and/or theresponsiveness of the beta band signals to electrical stimulation at oneor more positions, included in the therapy target definition.

As another example, controller 202 and/or controller 302 may selectparameters for forming a lesion based on the therapy target definition.For example, as discussed above, the therapy target definition mayindicate a spatial mapping of source 108 and controller 202 and/orcontroller 302 may select parameters for forming a lesion in a region ofbrain 108 corresponding to all or a portion of source 108 based on thespatial mapping. For example, therapy parameters (e.g., stimulationintensity and stimulation pulse width) that had maximally suppressed thebeta band signals during the spatial mapping can be used to estimate thevolume of tissue that is affected by the stimulation field. Theparticular lesion therapy parameters may be titrated such that thelesion size is targeted to substantially match the volume of tissueestimated by the spatial mapping process. Delivery of the lesion therapymay be performed through the same lead and electrodes used during thespatial mapping process. Alternatively, the lead used during the spatialmapping process may be removed, and a second lead placed atsubstantially the same location as the spatial mapping lead may be usedto deliver the lesion therapy at the appropriate location(s).

As another example, controller 202 and/or controller 302 may selectparameters for monitoring changes to source 108 and/or movement of lead114 or electrodes with respect to source 108. For example, controller202 and/or controller 302 may select parameters for monitoring aposition of source 108 with respect to lead 114 and/or electrodes basedon the therapy target definition.

Any suitable parameters may be selected based on the therapy targetdefinition. For example, appropriate electrodes or groups of electrodesmay be selected for delivery of therapy based on the therapy targetdefinition. As another example, voltage or current amplitude, frequency,and/or pulse width of electrical stimulation pulses may be selected fordelivery of therapy based on the therapy target definition. Asadditional examples, any suitable parameters for plasticity inductionsand/or drug infusions may be selected based on the therapy targetdefinition.

In some examples, a user may select any suitable therapy parametersbased on the therapy target definition. For example, a user may view agraphical or other representation of the therapy target definition viauser interface 304 and may input information indicating selection of oneor more therapy parameters based on the therapy target definition.

In some examples, defining the therapy target may comprise definingparameters, including, for example, selecting electrodes and/orintensities for delivering electrical stimulation for therapy, such thata separate step of selecting therapy parameters based on the therapytarget definition may not be necessary. In some examples, a separatestep of selecting therapy parameters may be performed to selectparameters that are some function of the parameters selected duringdefinition of the therapy target.

Therapy may be delivered to brain 106 of patient 104 based on theselected parameters (910). For example, in some examples, controller 202and/or controller 302 may control electrical stimulation circuitry 204to deliver the therapy to the brain 106 of the patient 104 based on theselected parameters.

For example, controller 202 and/or controller 302 may control deliveryof electrical stimulation for suppression of beta band signals based onthe selected parameters. In other examples, controller 202 and/orcontroller 302 may control delivery of electrical current, heat, cold,or chemical material for formation of a lesion, or for any othersuitable therapy, according to particular needs and based on theselected parameters. The selected parameters may facilitate efficacy indelivery of therapy. Controller 202 and/or controller 302 may also usethe selected parameters to monitor changes to source 108 and/or movementof lead 114 and/or electrodes with respect to source 108. For example,controller 202 and/or controller 302 may periodically define a therapytarget to determine any significant changes to the therapy targetdefinition, as may be indicated by the selected parameters, and changesmay indicate changes to source 108 and/or movement of lead 114 withrespect to source 108. Observed changes may be used to adjust or changetreatment accordingly.

Delivering therapy may include delivering electrical stimulation at theselected positions at the corresponding intensities determined to besuppressive at those positions. In other examples, delivering therapymay include delivering electrical stimulation at positions andintensities that are a function of the selected positions and/or theresponsiveness of the beta band signals to electrical stimulation at oneor more positions, respectively. For example, positions for delivery oftherapy and/or corresponding intensities for electrical stimulation fortherapy delivery may be based on the determined selected positions andthe determined suppressive stimulation intensities and may or may not beequivalent to those positions and intensities. Delivering therapy may,for example, suppress beta band signals corresponding to those positionsand/or may suppress unwanted symptoms in patient 104. As anotherexample, delivering therapy may include performing plasticity inductionsand/or drug infusions using parameters selected based on the therapytarget definition.

FIG. 10 is a flow diagram of another example technique for defining atherapy target, selecting therapy parameters based on the therapy targetdefinition, and delivering therapy to brain 106 of patient 104 based onthe selected parameters.

Electrical signals may be sensed at different positions when electricalstimulation is not delivered (1002). For example, sensing circuitry 206may sense electrical signals at the different positions when electricalstimulation is not delivered. For example, as described with referenceto FIGS. 4A-9, electrodes 118 corresponding to different axial positionsalong the length of a lead such as lead 114, and/or differentcircumferential positions about the circumference of the lead may beused to sense electrical signals when electrical stimulation is notdelivered at those positions. For example, local field potentials may besensed at each of those positions.

In some examples, a plurality of different positions for delivery of theelectrical stimulation may be selected based on the electrical signalssensed at the different positions when electrical stimulation is notdelivered (1004). For example, controller 202 and/or controller 302 mayselect a plurality of different positions for delivery of the electricalstimulation based on electrical signals sensed at the differentpositions when electrical stimulation is not delivered. For example, asdescribed with reference to FIGS. 4A-10, local field potentials over apredetermined threshold amount may be indicative of a position ofinterest such that controller 202 and/or controller 302 may selectpositions with local field potentials over the predetermined thresholdamount for electrical stimulation and, thus, further analysis. In otherexamples, the one or more positions of interest may be selected using asignal other than, or in addition to, a local field potential signal,such as a microelectrode recording. Moreover, the signal characteristicupon which the selection is based may be a characteristic other than, orin addition to, amplitude such as frequency, waveform morphology, powerlevel in a particular frequency band, or any other signal characteristicin the time domain or frequency domain.

Electrical stimulation may be delivered at a plurality of differentintensities at each of the selected plurality of different positionswithin brain 106 of patient 104 via selected combinations of electrodes108 (1006), as described in further detail with respect to FIG. 9. Aspreviously described, the selected positions for delivering electricalstimulation may be selected based on the sensed local field potentialscorresponding to those positions when electrical stimulation is notdelivered at those positions. The stimulation at different intensitiesmay be delivered as a progression of stimulation at increasingintensities until a predetermined level of suppression of a sensed betaband signal is sensed or until the beta band signal is maximallysuppressed. As stated above, some other signal characteristic instead ofor in addition to a beta band signal that is responsive to stimulationmay be monitored to determine when that signal characteristic isoptimally affected in some predetermined manner by the differentstimulation intensities. A signal characteristic may be optimallyaffected, for instance, when it decreases to some minimum, decreasesbelow some threshold or disappears entirely. In other examples, a signalcharacteristic may be optimally affected when it increases to somemaximum or increases above some threshold. In other cases, the signalcharacteristic may be considered to be optimally affected when itchanges in some other predetermined manner.

Electrical signals may be sensed at each of the different positionswithin brain 106 of patient 104 in response to the electricalstimulation delivered at each of the different intensities (1008), asdescribed in further detail with respect to FIG. 9.

A therapy target may be defined based on the sensed electrical signalsto provide a therapy target definition (1010), as described in furtherdetail with respect to FIG. 9. For example, controller 202 and/orcontroller 302 may define a therapy target based on the sensedelectrical signals. In some examples, definition of the therapy targetmay be further based on the electrical signals sensed when electricalstimulation is not delivered. For example, sensing local fieldpotentials to determine positions, and determining the responsiveness ofthe beta band signals to electrical stimulation for each position, maybe used to define a therapy target that is indicative of a spatialdefinition of a source, such as source 108. For example, a position thatis associated with a large local field potential and a large suppressivestimulation intensity may indicate a portion of source 108 adjacent tothe position that is substantially large. The local field potentialssensed when electrical stimulation is not delivered and theresponsiveness of the beta band signals to electrical stimulation foreach position may be used to develop a mapping of the spatial extent ofsource 108 that may be used for selection of therapy parameters to treator monitor source 108 and/or monitor movement of lead 114 and/orelectrodes with respect to source 108.

In some examples, the local field potentials sensed when electricalstimulation is not delivered and/or the responsiveness of the beta bandsignals to electrical stimulation for one or more positions may be usedto define a therapy target, the definition of which includes informationthat may be used to derive a mapping of the spatial extent of the source108 but may not itself include the mapping. For example, the therapytarget definition may include, for one or more positions, themeasurements of the local field potentials sensed when electricalstimulation is not delivered and/or the responsiveness of the beta bandsignals to electrical stimulation.

In some examples, the therapy target definition may include both amapping of the spatial extent of source 108 and/or other informationthat may be useful for selecting therapy parameters including, forexample, the responsiveness of the beta band signals to electricalstimulation at one more positions.

One or more parameters of therapy to be delivered to a brain of apatient may be selected based on the therapy target definition (1012),as also discussed with reference to FIG. 9. Therapy parameters may beselected based on a mapping of the spatial extent of source 108 and/orbased on other information in the definition of the therapy target. Forexample, parameters for forming a lesion and/or for monitoring source108 and/or the position of lead 114 and/or electrodes with respect tosource may be selected based on a mapping of the spatial extent ofsource 108. As another example, parameters for delivering electricalstimulation for treatment of source 108 may be selected based on theresponsiveness of the beta band signals to electrical stimulation. Forexample, selecting the parameters may include selecting intensities forelectrical stimulation that are equivalent to or some other function ofthe intensities determined to be suppressive.

Delivery of therapy to brain 106 of patient 104 may be controlled basedon the selected therapy parameters (1014), as discussed with referenceto FIG. 9. For example, controller 202 and/or controller 302 may controldelivery of therapy to brain 106 of patient 104 based on the therapytarget definition. A defined target that corresponds to a spatial extentof a source, such as source 108, may be used to deliver treatment usingelectrical stimulation for suppression of symptoms, including forforming a lesion, to monitor changes to source 108 and/or movement oflead 114 with respect to source 108, and/or for any other suitabletreatment or use according to particular needs.

Any suitable modifications to the described techniques may be madeaccording to particular needs. Although the techniques have beendescribed to include sensing of beta band signals, the technique mayinclude, alternatively or in addition, sensing of gamma band signals.For example, changes in sensed gamma band signals in response todelivery of electrical stimulation may also be used to define a therapytarget corresponding to a spatial extent of a source, such as source108. Sensing of other electrical signals that may change in response todelivery of electrical stimulation may also be used for defining thetherapy target according to particular needs. Additionally, delivery ofelectrical stimulation and sensing of electrical signals in response tothe delivery of electrical stimulation may be performed for one or morepositions before being performed at other positions. In some examples,these steps may be performed simultaneously for all positions. In someexamples, different electrodes or groups of electrodes may be used fordelivery of electrical stimulation and sensing of electrical signals. Inother examples, the same electrodes and/or groups of electrodes may beused for delivery of electrical stimulation and sensing of electricalsignals. In some examples, the same or different electrodes or groups ofelectrodes may be used for sensing of electrical signals before deliveryof electrical stimulation and for sensing of electrical signals inresponse to the delivery of electrical stimulation.

Additionally, multiple steps described as being performed by controller202 and/or controller 302 may be performed by either controller 202 orcontroller 302, both controller 202 and controller 302, and/or any othersuitable device or component according to particular needs.

In some examples, the positions for sensing local field potentialsand/or delivering electrical stimulation and sensing electrical signalsin response to the delivered electrical stimulation, may be adjacent toone other on a lead, whether axially adjacent or circumferentiallyadjacent. In other examples, the positions may not be adjacent to oneanother.

The techniques described in this disclosure, including those attributedto programmer 120, IMD 110, or various constituent components, may beimplemented, at least in part, in hardware, software, firmware or anycombination thereof. For example, various aspects of the techniques maybe implemented within one or more processors, including one or moremicroprocessors, DSPs, ASICs, FPGAs, or any other equivalent integratedor discrete logic circuitry, as well as any combinations of suchcomponents, embodied in programmers, such as physician or patientprogrammers, stimulators, image processing devices or other devices. Theterm “controller,” “processor” or “processing circuitry” may generallyrefer to any of the foregoing logic circuitry, alone or in combinationwith other logic circuitry, or any other equivalent circuitry.

Such hardware, software, firmware may be implemented within the samedevice or within separate devices to support the various operations andfunctions described in this disclosure. While the techniques describedherein are primarily described as being performed by controller 202 ofIMD 110 and/or controller 302 of programmer 120, any one or more partsof the techniques described herein may be implemented by a controller ofone of IMD 110, programmer 120, or another computing device, alone or incombination with each other.

In addition, any of the described units, modules or components may beimplemented together or separately as discrete but interoperable logicdevices. Depiction of different features as modules or units is intendedto highlight different functional aspects and does not necessarily implythat such modules or units must be realized by separate hardware orsoftware components. Rather, functionality associated with one or moremodules or units may be performed by separate hardware or softwarecomponents, or integrated within common or separate hardware or softwarecomponents.

When implemented in software, the functionality ascribed to the systems,devices and techniques described in this disclosure may be embodied asinstructions on a computer-readable medium such as RAM, ROM, NVRAM,EEPROM, FLASH memory, magnetic data storage media, optical data storagemedia, or the like. The instructions may be executed to support one ormore aspects of the functionality described in this disclosure.

Various embodiments of have been described. These and other embodimentsare within the scope of the following claims.

What is claimed is:
 1. A method for delivering therapy to a patient, themethod comprising: selecting one or more parameters of therapy to bedelivered to a brain of a patient, wherein the parameters are definedbased on: a first plurality of electrical signals sensed at each of aplurality of different positions within the brain of the patient whenelectrical stimulation is not delivered at each of the positions; and asecond plurality of electrical signals sensed at each of at least asubset of the plurality of different positions within the brain of thepatient in response to electrical stimulation delivered at each of theat least the subset of the positions at a plurality of differentintensities; and delivering the therapy to the brain of the patientbased on the selected parameters.
 2. The method of claim 1, furthercomprising determining a sequence for delivery of the electricalstimulation based on the first plurality of electrical signals.
 3. Themethod of claim 2, wherein determining a sequence for delivery of theelectrical stimulation based on the first plurality of electricalsignals comprises selecting a starting position of the plurality ofdifferent positions corresponding to a sensed electrical signal of thefirst plurality of sensed electrical signals having a measurement with ahighest value of measurements for each electrical signal of the firstplurality of electrical signals.
 4. The method of claim 1, furthercomprising: sensing the first plurality of electrical signals sensed ateach of the plurality of different positions within the brain of thepatient when the electrical stimulation is not delivered at each of thepositions; delivering the electrical stimulation at each of theplurality of different intensities at each of the at least a subset ofthe different positions; sensing the second plurality of electricalsignals at each of the at least a subset of the different positions inresponse to the electrical stimulation delivered at each of the at leasta subset of the different positions at the plurality of differentintensities; and defining the parameters based on the sensed first andsecond plurality of electrical signals and the delivered electricalstimulation.
 5. The method of claim 4, wherein the electricalstimulation comprises first electrical stimulation, and wherein:defining the parameters comprises: selecting at least some of thedifferent positions based on the sensed first and second plurality ofelectrical signals and the first electrical stimulation; and selectingintensities for each of respective positions of the at least some of thedifferent positions based on the sensed first and second plurality ofelectrical signals and the first electrical stimulation, and deliveringthe therapy to the brain of the patient based on the selected parameterscomprises delivering second electrical stimulation to the brain at eachof the at least some of the different positions at the intensitiesselected for each of the respective positions of the at least some ofthe different positions.
 6. The method of claim 5, further comprisingselecting the intensities for each of the respective positions of the atleast some of the different positions based on intensities of the firstelectrical stimulation delivered at the at least a subset of thedifferent positions.
 7. The method of claim 5, wherein the sensedelectrical signals comprise beta band signals, and selecting intensitiesfor each of the at least some of the different positions comprisesselecting intensities at which the first electrical stimulationsuppresses the sensed beta band signals by a greater amount relative toother intensities that are not selected.
 8. The method of claim 5,wherein the selected at least some of the different positions compriseall of the at least a subset of the different positions to which thefirst electrical stimulation was delivered.
 9. The method of claim 5,wherein delivering the second electrical stimulation to the brain ateach of the at least some of the different positions comprisesdelivering the second electrical stimulation via a plurality ofelectrodes implanted proximate to the respective positions of the atleast some of the different positions.
 10. The method of claim 9,wherein the electrodes are carried by a lead implanted in the patient.11. The method of claim 10, wherein sensing the first and secondplurality of electrical signals comprises sensing the first and secondplurality of electrical signals at each of the at least a subset of thedifferent positions via the plurality of electrodes implanted proximateto the respective positions of the at least a subset of the differentpositions.
 12. The method of claim 5, wherein sensing the first andsecond plurality of electrical signals comprises sensing the first andsecond plurality of electrical signals at each of the at least a subsetof the different positions via a plurality of electrodes implantedproximate to the respective positions of the at least a subset of thedifferent positions, and wherein the at least a subset of the differentpositions comprise combinations of a plurality of axial positions alonga length of the lead and a plurality of circumferential positions abouta circumference of the lead.
 13. The method of claim 5, wherein sensingthe first and second plurality of electrical signals comprises sensingthe first and second plurality of electrical signals at each of the atleast a subset of the different positions via a plurality of electrodesimplanted proximate to the respective positions of the at least a subsetof the different positions, and wherein the at least a subset of thedifferent positions comprise at least one of a plurality of axialpositions along a length of the lead or a plurality of circumferentialpositions about a circumference of the lead.
 14. The method of claim 5,wherein: defining the parameters based on the sensed first and secondplurality of electrical signals and the delivered electrical stimulationcomprises selecting at least some of the different positions based onthe sensed first and second plurality of electrical signals and thedelivered electrical stimulation, and delivering the therapy to thebrain of the patient based on the selected parameters comprisesdelivering electrical energy to the brain at each of the at least someof the different positions at intensities sufficient to form one or morelesions in the brain.
 15. The method of claim 4, wherein sensing thefirst and second plurality of electrical signals comprises sensing thefirst and second plurality of electrical signals at each of the at leasta subset of the different positions via a plurality of electrodesimplanted proximate to the respective positions of the at least a subsetof the different positions.
 16. The method of claim 4, wherein definingthe parameters based on the sensed first and second plurality ofelectrical signals and the delivered electrical stimulation comprisesdefining the parameters based on the sensed second plurality ofelectrical signals and intensities of the delivered electricalstimulation in response to which the second plurality of electricalsignals were sensed, wherein the intensities and the sensed secondplurality of electrical signals spatially define a source of the sensedelectrical signals within the brain of the patient.
 17. The method ofclaim 1, wherein the different positions are adjacent to one another.18. A system for delivering electrical stimulation, the systemcomprising: a plurality of electrodes; electrical stimulation circuitry;a controller configured to: select one or more parameters of therapy tobe delivered to a brain of a patient, wherein the parameters are definedbased on: a first plurality of electrical signals sensed at a pluralityof different positions within the brain of the patient when electricalstimulation is not delivered at each of the positions; and a secondplurality of electrical signals sensed at each of at least a subset ofthe different positions within the brain of the patient in response toelectrical stimulation delivered at each of the at least a subset of thedifferent positions at a plurality of different intensities; and controlthe electrical stimulation circuitry to deliver the therapy to the brainof the patient based on the selected parameters and via a first one ormore electrodes of the plurality of electrodes.
 19. The system of claim18, wherein the controller is further configured to determine a sequencefor delivery of the electrical stimulation based on the first pluralityof electrical signals.
 20. The system of claim 19, wherein thecontroller is further configured to determine the sequence for deliveryof the electrical stimulation based on the first plurality of electricalsignals by selecting a starting position of the plurality of differentpositions corresponding to a sensed electrical signal of the firstplurality of sensed electrical signals having a measurement with ahighest value of measurements for each electrical signal of the firstplurality of electrical signals.
 21. The system of claim 18, furthercomprising sensing circuitry, and wherein: the sensing circuitry isconfigured to sense the first plurality of electrical signals sensed ata plurality of different positions within the brain of the patient whenelectrical stimulation is not delivered at each of the positions; thecontroller is further configured to control the electrical stimulationcircuitry to deliver the electrical stimulation at each of the pluralityof different intensities at each of the at least a subset of thedifferent positions; the sensing circuitry is configured to sense thesecond plurality of electrical signals at each of the at least a subsetof the different positions in response to the electrical stimulationdelivered at each of the at least a subset of the different positions atthe plurality of different intensities; and the controller is furtherconfigured to define the parameters based on the sensed first and secondplurality of electrical signals and the delivered electricalstimulation.
 22. The system of claim 21, wherein the electricalstimulation comprises first electrical stimulation, and wherein: thecontroller is further configured to define the parameters by: selectingat least some of the different positions based on the sensed first andsecond plurality of electrical signals and the delivered firstelectrical stimulation; and selecting intensities for each of respectivepositions of the at least some of the different positions based on thesensed first and second plurality of electrical signals and thedelivered first electrical stimulation, and the controller is furtherconfigured to control the electrical stimulation circuitry to deliverthe therapy to the brain of the patient based on the selected parametersby delivering second electrical stimulation to the brain at each of theat least some of the different positions at the intensities selected foreach of the respective positions of the at least some of the differentpositions.
 23. The system of claim 22, wherein the controller is furtherconfigured to select the intensities for each of the respectivepositions of the at least some of the different positions based onintensities of the first electrical stimulation delivered at the atleast a subset of the different positions.
 24. The system of claim 22,wherein the sensed electrical signals comprise beta band signals, andthe controller is further configured to select intensities for each ofthe at least some of the different positions by selecting intensities atwhich the first electrical stimulation suppresses the sensed beta bandsignals by a greater amount relative to other intensities that are notselected.
 25. The system of claim 22, wherein the selected at least someof the different positions comprise all of the at least a subset of thedifferent positions to which the first electrical stimulation wasdelivered.
 26. The system of claim 22, wherein the controller is furtherconfigured to control the electrical stimulation circuitry to deliverthe second electrical stimulation to the brain at each of the at leastsome of the different positions by controlling the electricalstimulation circuitry to deliver the second electrical stimulation via aplurality of electrodes implanted proximate to the respective positionsof the at least some of the different positions.
 27. The system of claim26, wherein the electrodes are carried by a lead implantable in thepatient.
 28. The system of claim 27, wherein the sensing circuitry isfurther configured to sense the first and second plurality of electricalsignals by sensing the first and second plurality of electrical signalsat each of the at least a subset of the different positions via theplurality of electrodes implanted proximate to the respective positionsof the at least a subset of the different positions.
 29. The system ofclaim 22, wherein the sensing circuitry is further configured to sensethe first and second plurality of electrical signals by sensing thefirst and second plurality of electrical signals at each of the at leasta subset of the different positions via a plurality of electrodesimplantable proximate to the respective positions of the at least asubset of the different positions, and wherein the at least a subset ofthe different positions comprise combinations of a plurality of axialpositions along a length of the lead and a plurality of circumferentialpositions about a circumference of the lead.
 30. The system of claim 22,wherein the sensing circuitry is further configured to sense the firstand second plurality of electrical signals by sensing the first andsecond plurality of electrical signals at each of the at least a subsetof the different positions via a plurality of electrodes implantableproximate to the respective positions of the at least a subset of thedifferent positions, and wherein the at least a subset of the differentpositions comprise at least one of a plurality of axial positions alonga length of the lead or a plurality of circumferential positions about acircumference of the lead.
 31. The system of claim 22, wherein thecontroller is further configured to: define the parameters based on thesensed first and second plurality of electrical signals and thedelivered electrical stimulation by selecting at least some of thedifferent positions based on the sensed first and second plurality ofelectrical signals and the delivered electrical stimulation, and controlthe electrical stimulation circuitry to deliver the therapy to the brainof the patient based on the selected parameters by delivering electricalenergy to the brain at each of the at least some of the differentpositions at intensities sufficient to form one or more lesions in thebrain.
 32. The system of claim 21, wherein the sensing circuitry isfurther configured to sense the first and second plurality of electricalsignals by sensing the first and second plurality of electrical signalsat each of the at least a subset of the different positions via aplurality of electrodes implantable proximate to the respectivepositions of the at least a subset of the different positions.
 33. Thesystem of claim 21, wherein the controller is further configured todefine the parameters based on the sensed first and second plurality ofelectrical signals and the delivered electrical stimulation by definingthe parameters based on the sensed second plurality of electricalsignals and intensities of the delivered electrical stimulation inresponse to which the second plurality of electrical signals weresensed, wherein the intensities and the sensed second plurality ofelectrical signals spatially define a source of the sensed electricalsignals within the brain of the patient.
 34. The system of claim 18,wherein the different positions are adjacent to one another.
 35. Asystem for delivering electrical stimulation, the system comprising:means for selecting one or more parameters of therapy to be delivered toa brain of a patient, wherein the parameters are defined based on: afirst plurality of electrical signals sensed at a plurality of differentpositions within the brain of the patient when electrical stimulation isnot delivered at each of the positions; and a second plurality ofelectrical signals sensed at each of at least a subset of the differentpositions within the brain of the patient in response to electricalstimulation delivered at each of the at least a subset of the differentpositions at a plurality of different intensities; and means fordelivering the therapy to the brain of the patient; and means forcontrolling the means for delivering therapy to deliver the therapy tothe brain of the patient based on the selected parameters.
 36. Thesystem of claim 35, further comprising a means for determining asequence for delivery of the electrical stimulation based on the firstplurality of electrical signals.
 37. The system of claim 36, furthercomprising a means for determining the sequence for delivery of theelectrical stimulation based on the first plurality of electricalsignals by selecting a starting position of the plurality of differentpositions corresponding to a sensed electrical signal of the firstplurality of sensed electrical signals having a measurement with ahighest value of measurements for each electrical signal of the firstplurality of electrical signals.
 38. The system of claim 35, furthercomprising: means for sensing the first plurality of electrical signalsat a plurality of different positions within the brain of the patientwhen electrical stimulation is not delivered at each of the positions;means for delivering electrical stimulation; means for controlling themeans for delivering electrical to deliver the electrical stimulation ateach of the plurality of different intensities at each of the at least asubset of the different positions; means for the sensing the secondplurality of electrical signals at each of the at least a subset of thedifferent positions in response to the electrical stimulation deliveredat each of the at least a subset of the different positions at theplurality of different intensities; and means for defining theparameters based on the sensed first and second plurality of electricalsignals and the delivered electrical stimulation.
 39. The system ofclaim 38, wherein the electrical stimulation comprises first electricalstimulation, and further comprising: means for defining the parametersby: selecting at least some of the different positions based on thesensed first and second plurality of electrical signals and thedelivered electrical stimulation; and selecting intensities for each ofrespective positions of the at least some of the different positionsbased on the sensed first and second plurality of electrical signals andthe delivered electrical stimulation, and means for controlling themeans for delivering electrical stimulation to deliver the therapy tothe brain of the patient based on the selected parameters by deliveringsecond electrical stimulation to the brain at each of the at least someof the different positions at the intensities selected for each of therespective positions of the at least some of the different positions.40. The system of claim 39, further comprising means for selecting theintensities for each of the respective positions of the at least some ofthe different positions based on intensities of the electricalstimulation delivered at the different positions.